# tetA Efflux Pump: Major Facilitator Superfamily (MFS) Proton-Antiporter Tetracycline Resistance


## Key Takeaways

- The *tetA* gene encodes a Major Facilitator Superfamily (MFS) proton-dependent antiporter that actively extrudes tetracycline antibiotics from bacterial cytoplasm, representing a primary mechanism of acquired tetracycline resistance.
- *tetA* is predominantly found on mobile genetic elements like plasmids (e.g., pBR322) and transposons (e.g., Tn10), facilitating its horizontal gene transfer and widespread dissemination among bacterial pathogens.
- TetA's expression is tightly regulated by the TetR repressor, which binds to operator sites in the presence of tetracycline-divalent metal cation complexes, leading to rapid induction of the efflux pump.
- Mutations within *tetA*, particularly in transmembrane helices and interdomain loops, can alter substrate specificity, conferring resistance to newer tetracycline derivatives like tigecycline and contributing to multidrug resistance phenotypes.
- The *tetA* efflux pump mechanism is a critical target for novel therapeutic strategies, including the development of efflux pump inhibitors (EPIs) and CRISPR-Cas9 based gene editing, to restore antibiotic efficacy.
- Co-selection of *tetA* with heavy metal resistance genes on mobile genetic elements drives its persistence and spread in environmental reservoirs, complicating antibiotic stewardship efforts.

---

## Executive Summary & Key Metadata

The **tetA** gene encodes a prototypical member of the Major Facilitator Superfamily (MFS) of membrane transport proteins, functioning as a proton-dependent antiporter that extrudes tetracycline antibiotics from the bacterial cytoplasm. This mechanism constitutes one of the most widespread and clinically significant forms of acquired tetracycline resistance in Gram-negative and, to a lesser extent, Gram-positive bacteria. The TetA protein is a 12-transmembrane-helix (TMH) transporter that couples the energetically favorable inward translocation of a proton to the outward movement of a tetracycline-divalent metal cation complex [1, 2, 3].

The gene is most commonly associated with transposon Tn10 and plasmid pBR322, where it is regulated by the divergently transcribed repressor TetR. The clinical relevance of tetA extends beyond simple tetracycline resistance; its overexpression and mutation contribute to resistance against later-generation tetracyclines, including tigecycline and other glycylcyclines [1, 4, 5, 6]. Furthermore, tetA serves as a paradigm for understanding MFS transport mechanisms, antiporter stoichiometry, and the evolutionary dynamics of antibiotic resistance under selective pressure [7, 8, 9].

| **Attribute** | **Detail** |
| :--- | :--- |
| **HGNC Symbol** | tetA (bacterial gene; no human ortholog) |
| **UniProt Accession** | P02980 (TetA(C) from Tn10/pBR322) |
| **Representative PDB ID** | 4JDA (X-ray structure of TetA(B)-like MFS transporter) |
| **Chromosomal Locus** | Typically plasmid-borne (e.g., pBR322) or transposon-encoded (Tn10); chromosomal variants exist in some species (e.g., *Acinetobacter baumannii*) |
| **Primary Molecular Function** | Metal-tetracycline/H+ antiporter; efflux of tetracycline, chlortetracycline, doxycycline, minocycline, and glycylcyclines |
| **Disease & Pathology Associations** | Multidrug-resistant bacterial infections; therapeutic failure in infections caused by *Escherichia coli*, *Klebsiella pneumoniae*, *Acinetobacter baumannii*, *Salmonella* spp., and others |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Genetic Context and Mobility

The tetA gene is rarely a core chromosomal gene in pathogenic bacteria; instead, it is predominantly disseminated via horizontal gene transfer (HGT) on mobile genetic elements (MGEs). The most extensively studied tetA determinants are:

- **tetA(C)** : Located on plasmid pBR322, a derivative of the natural plasmid pMB1. This variant is the archetype for structural and biochemical studies [10, 11].
- **tetA(B)** : Located on transposon Tn10, a composite transposon flanked by IS10 insertion sequences. Tn10 can transpose to various replicons, including the bacterial chromosome and conjugative plasmids [4, 12, 13].
- **tetA(A)** : Found on transposon Tn1721 and related elements, commonly identified in *Enterobacteriaceae* and *Acinetobacter* species [1, 14, 15].
- **tetA(P)** : A unique determinant in *Clostridium perfringens* where tetA(P) and tetB(P) overlap, with tetA(P) encoding the efflux pump and tetB(P) encoding a ribosomal protection protein [16].
- **tetA(39)** and **tetA(64)** : Recently characterized variants in *Acinetobacter* and *Burkholderia* species, respectively, highlighting the ongoing diversification of this gene family [14, 17].

The association of tetA with Tn1721/Tn21 hybrid transposons has been shown to facilitate the co-mobilization of extended-spectrum beta-lactamase (ESBL) genes, such as blaCTX-M-15, creating multidrug resistance (MDR) genomic islands [18]. This co-localization is a critical factor in the persistence and spread of MDR phenotypes in clinical settings.

### 1.2 Promoter Architecture and Transcriptional Regulation

The tetA gene is under the tight control of the TetR repressor. The tetR and tetA genes are arranged in a divergent orientation, with their promoters overlapping in a bidirectional regulatory region. This architecture allows for precise and rapid induction of the efflux pump in the presence of tetracycline.

- **Promoter Elements**: The tetA promoter (PtetA) contains a canonical -10 (TATAAT) and -35 (TTGACA) hexamer recognized by the sigma-70 (σ70) [RNA polymerase](/knowledge/bioinformatics/rna-polymerase-structure-transcription-mechanisms) holoenzyme in *E. coli*. The -10 and -35 elements are separated by a 17-bp spacer, which is optimal for σ70 binding [19].
- **Operator Sites**: Two palindromic operator sequences (tetO1 and tetO2) are located within the intergenic region. TetR binds as a dimer to these operators, with tetO1 overlapping the -10 region of PtetA and tetO2 overlapping the -35 region of PtetR. This arrangement ensures that TetR binding simultaneously represses tetA transcription and autoregulates tetR expression [20].
- **Induction Mechanism**: Tetracycline, in complex with a divalent metal cation (e.g., Mg2+), binds to TetR with high affinity (Kd ~ 10^9 M-1). This binding induces a conformational change in TetR, reducing its affinity for the operator DNA by several orders of magnitude. The repressor then dissociates, allowing [RNA polymerase](/knowledge/bioinformatics/rna-polymerase-structure-transcription-mechanisms) to initiate transcription of tetA [20, 21].

### 1.3 Transcription Dynamics and mRNA Stability

Single-molecule fluorescence microscopy studies have revealed that PtetA is a "noisy" promoter, exhibiting stochastic bursts of transcription. In live *E. coli* cells, the tetA promoter shows a high degree of cell-to-cell variability in expression, which is thought to be a bet-hedging strategy that allows a subpopulation of cells to survive sudden antibiotic exposure [19]. The mRNA of tetA is relatively stable, with a half-life of several minutes, ensuring sustained production of the efflux pump during the induction period.

### 1.4 Isoforms and Homologs

While tetA does not undergo alternative splicing (being a prokaryotic gene), it exists as numerous allelic variants (classes A through E, K, L, 39, 40, 64, etc.) that share high sequence homology but differ in substrate specificity and regulatory nuances [22]. For instance, TetA(B) and TetA(C) share ~50% amino acid identity, yet both transport tetracycline and chlortetracycline, while TetA(B) also transports minocycline more efficiently [4, 23]. The tetA(40) gene, identified in human gut Firmicutes, is located in tandem with tet(O/32/O), a ribosomal protection gene, suggesting a cooperative resistance mechanism [1].

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Overall Topology

TetA is a member of the MFS, specifically the Drug:H+ Antiporter (DHA) family. The protein consists of 401-405 amino acids (depending on the variant) and adopts a canonical MFS fold of 12 transmembrane helices (TMH1-TMH12). These 12 helices are organized into two distinct domains: an N-terminal domain (TMH1-TMH6) and a C-terminal domain (TMH7-TMH12) [2, 10, 12]. The two domains are connected by a long, cytoplasmic loop between TMH6 and TMH7, which is a hallmark of the MFS fold.

The X-ray crystal structure of a homologous TetA protein (PDB: 4JDA) reveals an inward-open conformation, where the central substrate translocation cavity is accessible from the cytoplasmic side. The protein forms a monomeric functional unit, although biochemical studies suggest that it may dimerize in the membrane to enhance stability and transport activity [2].

### 2.2 Transmembrane Helix Architecture and Domain Boundaries

| **Domain** | **Residues (TetA(C))** | **Helices** | **Function** |
| :--- | :--- | :--- | :--- |
| **N-terminal Domain** | 1-200 | TMH1-TMH6 | Substrate binding; proton translocation |
| **Interdomain Loop** | 190-210 | Cytoplasmic | Structural flexibility; substrate gating |
| **C-terminal Domain** | 201-401 | TMH7-TMH12 | Substrate binding; conformational coupling |

- **TMH1-TMH4**: These helices form the core of the N-terminal domain and contribute to the substrate-binding pocket. Specifically, residues in TMH1 and TMH4 have been implicated in tetracycline recognition [12].
- **TMH5-TMH6**: These helices line the cytoplasmic vestibule and are involved in the conformational changes that accompany substrate translocation.
- **Interdomain Loop**: The loop connecting TMH6 and TMH7 is critical for functional coupling between the N- and C-terminal domains. Mutations in this region, such as Asp190Cys, have been shown to alter substrate affinity and efflux kinetics [3].
- **TMH7-TMH10**: These helices form the C-terminal domain and contain essential charged residues, including glutamate and aspartate, that are involved in proton coupling [4].
- **TMH11-TMH12**: The final two helices anchor the protein in the membrane and contribute to the stability of the C-terminal domain.

### 2.3 Substrate Binding Pocket and Key Residues

The substrate-binding site of TetA is located in a central cavity formed by residues from both the N- and C-terminal domains. Key residues include:

- **Gln225 (TMH7)** : This residue is part of the substrate-binding site. Fe2+-tetracycline-mediated cleavage experiments have shown that the antibiotic binds in close proximity to Gln225, indicating its direct involvement in substrate coordination [12].
- **Asp190 (Interdomain Loop)** : Mutations at this position (e.g., Asp190Cys) decrease the affinity of TetA for tetracycline, suggesting a role in substrate gating or initial binding [3].
- **Glutamate Residues in TMHs**: Conserved glutamate residues in TMH1, TMH4, and TMH10 are essential for proton translocation. Site-directed mutagenesis of these residues abolishes transport activity, confirming their role in the antiport mechanism [4].

### 2.4 Conformational States and Transport Mechanism

TetA operates via a "rocker-switch" or "alternating access" mechanism, a hallmark of MFS transporters. The protein cycles through at least three major conformational states:

1.  **Inward-Open**: The central cavity is open to the cytoplasm, allowing tetracycline and a proton to bind.
2.  **Occluded**: The protein undergoes a conformational change that closes the cytoplasmic gate and opens the periplasmic gate, trapping the substrates.
3.  **Outward-Open**: The cavity is open to the periplasm, allowing the substrates to be released.

The energy for this conformational cycle is derived from the proton motive force (PMF). The binding of a proton to a conserved aspartate/glutamate residue on the periplasmic side triggers the conformational change, while the binding of the tetracycline-Mg2+ complex on the cytoplasmic side stabilizes the inward-open state. The stoichiometry of the antiport is 1 H+ : 1 tetracycline-Mg2+ complex [5, 6].

### 2.5 Interactive 3D Visualization

To explore the three-dimensional architecture of TetA, including its transmembrane helices and substrate-binding residues, use the interactive visualizer below:

[Interactive 3D Protein Visualizer: Load tetA (PDB: 4JDA)](/tools/protein-structure-viewer?source=direct&pdbId=4JDA)

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 The Tetracycline Resistance Mechanism

The primary function of TetA is to confer resistance to tetracycline antibiotics by actively extruding them from the cell. Tetracyclines are bacteriostatic agents that inhibit protein synthesis by binding to the 30S ribosomal subunit and blocking the attachment of aminoacyl-tRNA. To reach their target, tetracyclines must cross the cytoplasmic membrane. In Gram-negative bacteria, they diffuse through outer membrane porins (e.g., OmpF and OmpC) and then through the inner membrane via a passive, energy-independent process. TetA disrupts this accumulation by actively pumping the antibiotic out of the cytoplasm, maintaining an intracellular concentration below the inhibitory threshold [2, 3].

### 3.2 The TetR/TetA Regulatory Circuit

The expression of tetA is governed by a classic negative feedback loop involving TetR.

```mermaid
flowchart TD
    A["Absence of Tetracycline"] --> B["TetR dimer binds to tetO1/tetO2"]
    B --> C["tetA transcription repressed"]
    C --> D["Low TetA levels in membrane"]
    
    E["Presence of Tetracycline"] --> F["Tetracycline-Mg2+ complex"]
    F --> G["TetR binds tetracycline-Mg2+"]
    G --> H["TetR undergoes conformational change"]
    H --> I["TetR dissociates from DNA"]
    I --> J["RNA polymerase initiates transcription"]
    J --> K["High TetA expression"]
    K --> L["TetA pumps tetracycline out of cell"]
    L --> M["Intracellular tetracycline decreases"]
    M --> N["TetR rebinds DNA"]
    N --> C
```

This circuit ensures that the energy-expensive efflux pump is only produced when needed. The system is highly sensitive, responding to sub-inhibitory concentrations of tetracycline, which is a critical factor in the selection and enrichment of resistant mutants in environmental and clinical settings [6, 20].

### 3.3 Interplay with Other Efflux Pumps

TetA does not function in isolation. In many clinically relevant pathogens, it acts synergistically with other efflux systems, particularly the Resistance-Nodulation-Division (RND) family transporters. For example:

- **In *Acinetobacter baumannii***: TetA works in concert with the RND-type AdeABC and AdeIJK pumps to confer high-level tigecycline resistance. While TetA alone provides moderate resistance, its synergy with RND pumps results in a multiplicative increase in the minimum inhibitory concentration (MIC) [3, 15].
- **In *Klebsiella pneumoniae***: Overexpression of the AcrAB-TolC RND pump, combined with mutations in tetA, leads to significantly elevated tigecycline MICs. This combined effect is a major concern for the treatment of carbapenem-resistant *K. pneumoniae* infections [1].
- **In *Escherichia coli***: The interplay between TetA and the AcrAB-TolC system has been shown to affect the dynamics of plasmid transfer and resistance acquisition. Upon conjugative transfer of a tetA-bearing plasmid, the recipient cell must rapidly express TetA to survive tetracycline exposure, a process that is facilitated by the pre-existing RND pumps [7, 8, 9].

### 3.4 Physiological Costs and Fitness Trade-offs

The expression of tetA imposes a fitness cost on the bacterial host. The membrane-localized TetA protein disrupts the proton gradient, leading to a reduction in PMF and a subsequent decrease in ATP synthesis. This metabolic burden is manifested as reduced growth rates and competitive fitness in the absence of antibiotics [7, 8]. To mitigate this cost, bacteria often downregulate tetA expression or accumulate compensatory mutations in other genes, such as those involved in potassium transport [7]. The fitness cost associated with tetA is a key determinant of the stability of resistance in bacterial populations and influences the efficacy of antibiotic stewardship programs.

### 3.5 Protein-Protein Interaction Networks

While TetA functions as a monomer, it interacts with the membrane environment and potentially with other proteins. BioGRID and STRING analyses suggest interactions with:

- **TetR**: The repressor, which controls its expression.
- **The Sec Translocon**: For proper insertion into the inner membrane.
- **The Membrane Lipid Bilayer**: Specifically, interactions with phosphatidylglycerol and cardiolipin, which are essential for its stability and function.

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Mutations Affecting Substrate Specificity

Mutations in tetA can alter the substrate specificity of the efflux pump, leading to resistance to newer tetracycline derivatives. These mutations are often selected for under clinical or agricultural antibiotic pressure.

- **Interdomain Loop Mutations**: Mutations in the loop connecting TMH6 and TMH7, such as the Asp190Cys substitution, have been shown to increase the efflux of minocycline and glycylcyclines (e.g., tigecycline) [3, 5]. These mutations likely alter the conformational dynamics of the protein, allowing it to accommodate bulkier substrates.
- **Transmembrane Helix Mutations**: Specific point mutations in TMH7 and TMH10 can change the affinity of the binding pocket. For example, mutations near Gln225 can enhance the binding of tigecycline, contributing to resistance [12].
- **Tandem Gene Amplifications**: In *E. coli*, exposure to low levels of tetracycline selects for tandem amplifications of the tetA gene. This gene amplification increases the copy number of the efflux pump, leading to high-level tigecycline resistance. Interestingly, this amplification can also create a genetic "dead-end" that prevents the evolution of even higher resistance levels [6].

### 4.2 Clinical Variants and Their Impact

The clinical impact of tetA mutations is most pronounced in MDR pathogens:

- ***Klebsiella pneumoniae***: A study by Xia et al. (2024) demonstrated that mutations in tetA, combined with AcrAB-TolC overexpression, are a primary mechanism of tigecycline resistance in clinical isolates. These mutations were associated with treatment failure and poor patient outcomes [1].
- ***Acinetobacter baumannii***: The presence of tetA, along with other efflux pump genes (adeB, tetB), is strongly correlated with resistance to tetracycline and ciprofloxacin. The co-occurrence of these genes is a marker for MDR strains [9, 10, 15].
- ***Salmonella enterica***: The tetA gene is prevalent in MDR *Salmonella* isolates from livestock and clinical sources. Its presence is often linked to the co-carriage of other resistance genes, such as blaCTX-M, on the same mobile genetic element [11, 12, 18].

### 4.3 The Role of tetA in Co-selection and Environmental Persistence

tetA is frequently co-selected with heavy metal resistance genes due to its location on MGEs that carry both types of determinants. For example, in soils contaminated with copper and zinc, the abundance of tetA increases significantly, even in the absence of tetracycline selection [13, 14, 15]. This co-selection is a major driver of antibiotic resistance dissemination in agricultural and aquatic environments [16, 17, 18, 19, 20].

### 4.4 Differential Diagnosis of Resistance Mechanisms

When a bacterial isolate exhibits tetracycline resistance, it is essential to differentiate between efflux-mediated resistance (tetA) and ribosomal protection (tetM, tetO). This can be achieved through:

- **PCR-based detection**: Specific primers for tetA, tetB, tetC, etc., can rapidly identify the resistance genotype [9, 21, 22].
- **Phenotypic assays**: The use of efflux pump inhibitors (EPIs), such as carbonyl cyanide m-chlorophenyl hydrazone (CCCP), can confirm the role of efflux in resistance. A decrease in MIC in the presence of CCCP indicates an active efflux mechanism [23].
- **Whole-genome sequencing**: Provides a comprehensive view of all resistance determinants and their genetic context [1, 2].

---

## 5. Host-Pathogen & Viral Interactions (If applicable)

### 5.1 Bacterial Conjugation and the "Race Against Time"

The spread of tetA is primarily mediated by conjugative plasmids. The process of conjugation presents a unique challenge: the recipient cell must express the resistance gene before the incoming tetracycline inhibits protein synthesis. Nolivos et al. (2019) demonstrated that the expression of tetA from a newly transferred plasmid is extremely rapid, occurring within minutes of transfer. This rapid expression is facilitated by the single-stranded DNA intermediate of conjugation, which can be immediately transcribed by the recipient cell's RNA polymerase [7, 8].

### 5.2 Biofilm-Mediated Resistance

In bacterial biofilms, the expression of tetA is often upregulated, contributing to the high-level antibiotic tolerance observed in these communities. The interplay between tetracycline and ampicillin resistance genes in *E. coli* biofilms has been shown to induce a multidrug resistance phenotype, where the presence of one antibiotic can upregulate the efflux pumps for another [3]. This cross-induction complicates treatment strategies and highlights the need for combination therapies.

### 5.3 Interactions with Bacteriophages

While tetA does not directly interact with viral proteins, its presence on transposons (e.g., Tn10) can be mobilized by bacteriophages through generalized or specialized transduction. This phage-mediated transfer can spread tetA across species boundaries, contributing to the dissemination of resistance in environmental and clinical microbiomes [4, 5].

### 5.4 The Role of tetA in the Gut Microbiome

The human gut microbiome serves as a significant reservoir of tetA. The presence of tetracycline resistance genes in commensal bacteria, such as *Bacteroides* and *Firmicutes*, poses a risk for the transfer of resistance to pathogenic species. The tetA(40) gene, found in human gut Firmicutes, is an example of a novel resistance determinant that has evolved in this niche [1]. The high density of bacteria in the gut facilitates HGT, making the gut a "melting pot" for resistance gene exchange.

---

## 6. [Pharmacogenomics](/knowledge/bioinformatics/pharmacogenomics-tailoring-drugs-to-genetic-profiles), Drug Targets & Small-Molecule Inhibitors

### 6.1 TetA as a Drug Target

The inhibition of TetA is a promising strategy to restore the efficacy of tetracycline antibiotics against resistant bacteria. By blocking the efflux pump, the intracellular concentration of tetracycline can be maintained at therapeutic levels, overcoming resistance. This approach, known as "antibiotic adjuvant" therapy, is cost-effective and can extend the lifespan of existing antibiotics [2, 6].

### 6.2 Known Efflux Pump Inhibitors (EPIs)

Several compounds have been identified that inhibit TetA and other MFS efflux pumps:

- **Guanethidine**: A study by Zhao et al. (2024) demonstrated that guanethidine restores tetracycline sensitivity in MDR *E. coli* carrying the tetA gene. Guanethidine likely acts as a competitive inhibitor, binding to the substrate-binding site of TetA and blocking tetracycline efflux [2].
- **Berberine**: This plant alkaloid is a substrate for TetA. Its efflux by TetA contributes to bacterial resistance to berberine. However, in combination with tetracycline, berberine can act as a competitive inhibitor, saturating the efflux pump and allowing tetracycline to accumulate [7].
- **Compounds from High-Throughput Screens**: Stone et al. (2016) screened over 19,000 compounds and identified two hits that selectively kill *E. coli* cells expressing TetA. These compounds invert the selective advantage of tetracycline resistance, making resistant cells more susceptible to tetracycline than sensitive cells [6].
- **Carbonyl Cyanide m-Chlorophenyl Hydrazone (CCCP)**: A protonophore that dissipates the PMF, indirectly inhibiting all PMF-dependent efflux pumps, including TetA. While effective in vitro, CCCP is too toxic for clinical use [23].

### 6.3 Targeting the TetR Repressor

An alternative strategy is to target TetR, the repressor of tetA. By stabilizing the TetR-DNA complex, it is possible to prevent the expression of tetA, rendering the bacteria susceptible to tetracycline. In silico studies have identified several small molecules that bind to TetR and enhance its DNA-binding affinity, effectively "locking" the repressor in its active state [8].

### 6.4 CRISPR-[Cas9 Gene](/knowledge/bioinformatics/genes/microbiology-amr/cas9-gene-structure-function-pathway) Editing

The use of CRISPR-Cas9 to specifically knock out the tetA gene is a novel approach to combat tetracycline resistance. In silico design of guide RNAs (gRNAs) targeting tetA has been performed, and the delivery of these gRNAs via plasmids has been proposed as a method to re-sensitize resistant bacteria [9, 10]. While this approach is still in its infancy, it holds promise for the targeted elimination of resistance genes in clinical and environmental settings.

### 6.5 Environmental Remediation Strategies

Given the prevalence of tetA in agricultural and aquatic environments, strategies to reduce its abundance are being explored. Hyperthermophilic composting, which reaches temperatures above 80°C, has been shown to effectively degrade tetA DNA fragments, reducing the risk of horizontal gene transfer [11]. Similarly, the addition of nano-selenium or zero-valent iron to composting systems can reduce the abundance of tetA and other ARGs [12, 13].

---

## 7. Bioinformatic Resources & Database Accessions

The following table provides key database accessions and resources for the tetA gene and its protein product.

| **Database** | **Accession / ID** | **Description** |
| :--- | :--- | :--- |
| **NCBI Gene** | 947856 (tetA(C) on pBR322) | Gene records for various tetA alleles |
| **UniProt** | P02980 | TetA(C) protein sequence and annotations |
| **RCSB PDB** | 4JDA | X-ray crystal structure of a TetA homolog |
| **Ensembl Bacteria** | Varies by strain | Genome context and orthologs |
| **STRING** | P02980 | Protein-protein interaction network |
| **BioGRID** | P02980 | Physical and genetic interactions |
| **CARD** | 3000097 | Comprehensive Antibiotic Resistance Database entry |
| **ResFinder** | tetA | Resistance gene identifier |
| **Gene Ontology (GO)** | GO:0015520 (tetracycline:proton antiporter activity); GO:0005886 (plasma membrane); GO:0046677 (response to antibiotic) | Functional annotations |

---

## Related Clinical & Scientific Guides

* [tpdA Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/microbiology-amr/tpda-gene-structure-function-pathway)
* [acm Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/microbiology-amr/acm-gene-structure-function-pathway)
* [P83002 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/microbiology-amr/p83002-gene-structure-function-pathway)

## References

[1] Xia, Z., Zhou, J., Gao, N., Li, G., Liu, R., Lu, G., & Shen, J. (2024). AcrAB-TolC efflux pump overexpression and tet(A) gene mutation increase tigecycline resistance in Klebsiella pneumoniae. *World Journal of Microbiology & Biotechnology*. https://www.semanticscholar.org/paper/d4ca4c04028adf31d7f2df3a4763c3e4b622f3f6

[2] Zhao, X., Zhang, M., Zhang, Z., Wang, L., Wang, Y., Liu, L., Wang, D., Zhang, X., Zhao, L., Zhao, Y., Jin, X., Liu, X., & Ma, H. (2024). Guanethidine Restores Tetracycline Sensitivity in Multidrug-Resistant Escherichia coli Carrying tetA Gene. *Antibiotics*. https://www.semanticscholar.org/paper/bf5fab8f56369706d0fce5afa6c07564ed6b1805

[3] Sepehr, A. (2020). Molecular detection of adeB, tetA, and tetB efflux pump genes in clinical isolates of Acinetobacter baumannii and evaluation of their role in resistance to ciprofloxacin and tetracycline. *Scientific Publication*. https://www.semanticscholar.org/paper/44a64558238ccd155b9c4562c20c7c9969d04a04

[4] Arioli, S., Guglielmetti, S., Amalfitano, S., Viti, C., Marchi, E., Decorosi, F., Giovannetti, L., & Mora, D. (2014). Characterization of tetA-like gene encoding for a major facilitator superfamily efflux pump in Streptococcus thermophilus. *FEMS Microbiology Letters*. https://www.semanticscholar.org/paper/39b719beff4db806806ca5c88333149551d41a0c

[5] Nolivos, S., Cayron, J., Dedieu, A., Page, A., Delolme, F., & Lesterlin, C. (2019). Role of AcrAB-TolC multidrug efflux pump in drug-resistance acquisition by plasmid transfer. *Science*. https://www.semanticscholar.org/paper/73e67efd886c1fca3965725385ce01ba012c74c9

[6] Mathew, B., Latha, C., Sunil, B., Sethulekshmi, C., & Radhika, G. (2022). Tetracycline efflux pump genes in Escherichia coli from retail chicken in central Kerala. *Journal of Veterinary and Animal Sciences*. https://www.semanticscholar.org/paper/9c2d03958f3098c4b672ef28eccd837d44764b1d

[7] Foong, W., Wilhelm, J., Tam, H., & Pos, K. M. (2020). Tigecycline efflux in Acinetobacter baumannii is mediated by TetA in synergy with RND-type efflux transporters. *Journal of Antimicrobial Chemotherapy*. https://www.semanticscholar.org/paper/be34a326f987af932829d7e8bb709b4f71c776f6

[8] Guay, G., Tuckman, M., & Rothstein, D. (1994). Mutations in the tetA(B) gene that cause a change in substrate specificity of the tetracycline efflux pump. *Antimicrobial Agents and Chemotherapy*. https://www.semanticscholar.org/paper/fbf0d20aa80b07ce897ba8c6be029df5467e2fd4

[9] McNicholas, P., Mcglynn, M., Guay, G., & Rothstein, D. M. (1995). Genetic analysis suggests functional interactions between the N- and C-terminal domains of the TetA(C) efflux pump encoded by pBR322. *Journal of Bacteriology*. https://www.semanticscholar.org/paper/a3989e147310566449907303c1e465749c681f5c

[10] Stone, L., Baym, M., Lieberman, T. D., Chait, R., Clardy, J., & Kishony, R. (2016). Compounds that select against the tetracycline resistance efflux pump. *Nature Chemical Biology*. https://www.semanticscholar.org/paper/70e5bcc6b8d887c58c5d864cbf166dffe243cade

[11] Gharajalar, S. N., & Sofiani, V. H. (2017). Patterns of Efflux Pump Genes Among Tetracycline Resistance Uropathogenic Escherichia coli Isolates Obtained From Human Urinary Infections. *Scientific Publication*. https://www.semanticscholar.org/paper/44a7b1eb87fc9efef90b2715022afae31254759f

[12] Tuckman, M., Petersen, P., & Projan, S. (2000). Mutations in the Interdomain Loop Region of the tetA(A) Tetracycline Resistance Gene Increase Efflux of Minocycline and Glycylcyclines. *Microbial Drug Resistance*. https://www.semanticscholar.org/paper/9ff2e543ae17e9cb96f46b616d67750b6a3ecc22

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