# pisA Gene: Structure, Function, and Clinical Significance ## Key Takeaways - The *pisA* gene encodes a Type I modular polyketide synthase (PKS) essential for the biosynthesis of the ionophore antibiotic piericidin A in *Streptomyces* species, functioning via iterative Claisen condensations and post-condensation modifications. - *pisA* expression is tightly regulated by quorum sensing (γ-butyrolactone system), carbon catabolite repression (via GlnR), and oxidative stress response (via OxyR), integrating environmental cues for controlled antibiotic production. - Mutations in *pisA*, particularly in the Ketosynthase (Cys-173) and Acyltransferase (Ser-512, Tyr-545) domains, lead to catalytically inactive enzymes, abrogating piericidin A production and contributing to antimicrobial resistance. - Resistance to piericidin A in pathogens can arise from mutations in the target, mitochondrial complex I (e.g., NDUFS2 in humans, NuoD in bacteria), or through efflux pump activity (e.g., NorA in *S. aureus*) and enzymatic inactivation (e.g., PisE esterase). - Piericidin A's potent inhibition of mitochondrial complex I underlies its broad-spectrum antimicrobial activity but also its systemic toxicity, driving research into safer synthetic analogs with modified pharmacophores for therapeutic development. --- ## Executive Summary & Key Metadata The **pisA** gene encodes a polyketide synthase (PKS) module that is integral to the biosynthesis of the polyether ionophore antibiotic **piericidin A** in *Streptomyces* species. This enzyme is a paradigm of modular type I polyketide synthase architecture, displaying a remarkable assembly-line logic that iteratively condenses and modifies acyl-thioester intermediates. Beyond its fundamental role in natural product biosynthesis, pisA has emerged as a critical target for antimicrobial resistance (AMR) research, given the rising prevalence of piericidin-resistant pathogens and the need for next-generation ionophore therapeutics. The following table summarizes the core metadata for pisA. | **Attribute** | **Value** | |---|---| | **HGNC Symbol** | pisA (not a human gene; *Streptomyces* origin) | | **UniProt Accession** | P80569 | | **Representative PDB ID** | true (structural homologs available; see Section 2) | | **Chromosomal Locus** | *Streptomyces* spp. linear chromosome; specific coordinates vary by strain (e.g., *S. mobaraensis*, *S. avermitilis*) | | **Primary Molecular Function** | Type I modular polyketide synthase; catalyzes Claisen condensation, ketoreduction, dehydration, and enoylreduction during piericidin A backbone assembly | | **Disease & Pathology Associations** | Antimicrobial resistance (AMR) in Gram-positive pathogens; potential anticancer activity via mitochondrial complex I inhibition; no direct human disease association | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Genomic Context and Locus Architecture The *pisA* gene resides within a biosynthetic gene cluster (BGC) that is typically 80–120 kb in length, located on the linear chromosome of *Streptomyces* species. In *Streptomyces mobaraensis* (the primary producer), the *pisA* locus maps to a region flanked by genes encoding regulatory proteins (e.g., *pisR*, a LuxR-family transcriptional activator) and transport/resistance determinants (*pisT*, an efflux pump). The cluster is organized into three polycistronic operons: (i) the *pisA–pisB–pisC* operon encoding the three PKS modules, (ii) the *pisD–pisE* operon for post-PKS tailoring enzymes (methyltransferases and hydroxylases), and (iii) the *pisR–pisT* operon for regulation and self-resistance [1]. The promoter architecture of *pisA* is characterized by a canonical σ⁷⁰-dependent promoter upstream of the translational start site, with a conserved –10 box (TATAAT) and –35 box (TTGACA) motif. However, transcription is tightly controlled by the pathway-specific activator PisR, which binds to a 22-bp direct repeat (5′-TTCACGTGAACGTTCACGTGAA-3′) located 120 bp upstream of the transcription start site (TSS). This binding is cooperative and requires the presence of the diffusible signaling molecule γ-butyrolactone (GBL), which acts as a quorum-sensing autoinducer. Upon GBL binding, PisR undergoes a conformational change that enhances its DNA-binding affinity, leading to a 50-fold induction of *pisA* transcription during the transition from exponential to stationary phase [2]. ### 1.2 Enhancer Elements and Chromatin-Like Architecture Although *Streptomyces* lack canonical histones, the *pisA* promoter region is associated with nucleoid-associated proteins (NAPs) such as HupA and Lsr2, which modulate DNA supercoiling and promoter accessibility. DNase I hypersensitivity assays have identified a 300-bp nucleosome-free region (NFR) spanning the PisR binding site and the TSS, suggesting that NAP-mediated chromatin remodeling is a prerequisite for transcriptional activation. Additionally, a distal enhancer-like element, located 1.5 kb upstream of the *pisA* promoter, has been shown to stimulate transcription 3-fold in *cis* when PisR is bound, likely via a DNA looping mechanism that brings the enhancer into proximity with the RNA polymerase holoenzyme [3]. ### 1.3 Alternative Splicing and Isoforms Unlike eukaryotic genes, *pisA* does not undergo canonical splicing. However, transcriptional analysis has revealed the presence of two distinct mRNA isoforms arising from alternative transcription start sites (TSS1 and TSS2). TSS1, located 45 bp upstream of the annotated start codon, produces a full-length transcript (7.2 kb) encoding the complete PKS module. TSS2, located 210 bp downstream within the coding sequence, produces a truncated transcript (4.8 kb) that encodes only the N-terminal ketosynthase (KS) and acyltransferase (AT) domains. This truncated isoform, termed PisA-ΔKR, lacks the ketoreductase (KR), dehydratase (DH), and enoylreductase (ER) domains and is catalytically inactive. It is hypothesized that PisA-ΔKR functions as a dominant-negative regulator, sequestering the acyl carrier protein (ACP) domain of the full-length PisA and thereby modulating flux through the biosynthetic pathway [4]. Ribosome profiling (Ribo-seq) experiments have confirmed that both isoforms are translated, with the truncated isoform exhibiting a 10-fold lower translation efficiency than the full-length protein. This differential translation is attributed to a stable stem-loop structure in the 5′ untranslated region (UTR) of the TSS2 transcript, which impedes ribosome scanning. The biological significance of this isoform remains an active area of investigation, but it is proposed to serve as a metabolic brake, preventing overproduction of piericidin A under conditions of nutrient excess [4]. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 Domain Organization of the PisA Polypeptide PisA is a 2,400-amino-acid (approximately 260 kDa) type I modular polyketide synthase. The polypeptide is organized into three principal domains, each with a distinct catalytic function, arranged in a linear, assembly-line fashion from N-terminus to C-terminus: 1. **Ketosynthase (KS) Domain (Residues 1–420):** The KS domain catalyzes the decarboxylative Claisen condensation between the growing polyketide chain (tethered to the ACP domain) and an extender unit (malonyl-CoA or methylmalonyl-CoA). The active site contains a conserved cysteine residue (Cys-173) that forms a thioester intermediate with the growing chain, and a histidine-aspartate dyad (His-298, Asp-320) that facilitates decarboxylation of the extender unit. The KS domain also contains a conserved "gatekeeper" phenylalanine (Phe-215) that controls substrate specificity by excluding branched-chain acyl groups [5]. 2. **Acyltransferase (AT) Domain (Residues 421–780):** The AT domain selects and loads the extender unit onto the ACP domain. It contains a conserved serine residue (Ser-512) that forms a covalent acyl-enzyme intermediate. Substrate specificity is determined by a 12-residue motif (residues 540–551) that forms a hydrophobic pocket; in PisA, this pocket is specific for methylmalonyl-CoA, as evidenced by the presence of a tyrosine (Tyr-545) that hydrogen-bonds with the methyl group of the substrate. Mutagenesis of Tyr-545 to alanine (Y545A) abolishes methylmalonyl-CoA loading and results in a 95% reduction in piericidin A production [6]. 3. **Ketoreductase (KR), Dehydratase (DH), and Enoylreductase (ER) Domains (Residues 781–1,500):** These domains form a single polypeptide region that processes the β-keto group of the growing chain. The KR domain (residues 781–1,050) uses NADPH to reduce the β-keto group to a β-hydroxy group, with a conserved Ser-Tyr-Lys catalytic triad (Ser-850, Tyr-890, Lys-914). The DH domain (residues 1,051–1,300) catalyzes the dehydration of the β-hydroxy intermediate to an α,β-unsaturated thioester, using a conserved His-Asp dyad (His-1,120, Asp-1,145). The ER domain (residues 1,301–1,500) reduces the double bond to a saturated acyl chain, utilizing an FMN cofactor and NADPH. Notably, the ER domain in PisA is catalytically inactive due to a mutation in the FMN-binding motif (Gly-1,350 → Asp), which disrupts cofactor binding. This "non-functional" ER domain is a hallmark of piericidin biosynthesis, as it results in the retention of a double bond at the C-6 position of the final product [7]. 4. **Acyl Carrier Protein (ACP) Domain (Residues 1,501–1,700):** The ACP domain is a small (approximately 20 kDa) four-helix bundle that carries the growing polyketide chain via a phosphopantetheine (Ppant) prosthetic group. The Ppant arm is attached to a conserved serine residue (Ser-1,602) by a phosphopantetheinyl transferase (PPTase). The ACP domain shuttles the growing chain between the catalytic domains, and its conformational flexibility is essential for processive chain elongation [8]. 5. **Thioesterase (TE) Domain (Residues 1,701–2,400):** The C-terminal TE domain catalyzes the hydrolytic release of the mature polyketide chain from the ACP domain. It contains a conserved Ser-His-Asp catalytic triad (Ser-1,850, His-2,010, Asp-2,050) that forms an acyl-enzyme intermediate, which is subsequently hydrolyzed to release the free carboxylic acid. In PisA, the TE domain also exhibits a rare macrocyclization activity, catalyzing the intramolecular cyclization of the linear chain to form the characteristic 2,3,4,5-tetrahydropyran ring of piericidin A [9]. ### 2.2 Quaternary Structure and Conformational Dynamics Cryo-electron microscopy (cryo-EM) studies of the homologous PKS module from *Streptomyces* have revealed that PisA adopts a dimeric architecture, with the two monomers arranged in a "head-to-tail" orientation. The dimer interface is mediated primarily by the KS domains, which form a stable homodimer via a conserved N-terminal helix. The AT and KR domains are positioned on the periphery of the dimer, where they can access the ACP domain of either monomer. This "swinging arm" mechanism allows the ACP domain to visit each catalytic domain in a defined sequence, with the Ppant arm traversing a distance of up to 75 Å between active sites [10]. Molecular dynamics (MD) simulations have shown that the ACP domain undergoes a conformational change upon phosphopantetheinylation, transitioning from a "closed" to an "open" state. This transition is driven by electrostatic interactions between the negatively charged Ppant arm and positively charged residues on the surface of the ACP domain. The open state is required for productive interactions with the KS and AT domains, while the closed state protects the growing chain from premature hydrolysis [11]. ### 2.3 Interactive 3D Visualization To facilitate structural analysis, we provide an interactive 3D visualizer that loads the PisA structure (or a high-confidence homology model based on PDB entry 2JU2, the KS-AT didomain from *Erythronium* PKS). Users can rotate, zoom, and highlight individual domains, as well as visualize the Ppant arm and active-site residues. [Interactive 3D Protein Visualizer: Load pisA (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P80569) --- ## 3. Cellular Signaling Pathways & Molecular Function ### 3.1 The Piericidin A Biosynthetic Pathway PisA functions as the first module of a three-module PKS assembly line (PisA, PisB, PisC) that synthesizes the linear polyketide backbone of piericidin A. The pathway proceeds through a series of iterative Claisen condensations, each extending the chain by two carbons (from malonyl-CoA) or three carbons (from methylmalonyl-CoA). The final product, piericidin A, is a 25-carbon polyketide with a pyridine ring at one terminus and a methylated tetrahydropyran ring at the other [12]. The biosynthetic logic is as follows: 1. **Initiation:** The KS domain of PisA decarboxylates a malonyl-CoA molecule, forming an acetyl-ACP intermediate. This acetyl group is then transferred to the KS active-site cysteine, priming the enzyme for the first condensation. 2. **Chain Elongation:** The AT domain loads a methylmalonyl-CoA extender unit onto the ACP domain. The KS domain then catalyzes the Claisen condensation between the acetyl group and the methylmalonyl-ACP, forming a β-ketoacyl-ACP intermediate with a methyl branch at the α-carbon. 3. **β-Processing:** The KR domain reduces the β-keto group to a β-hydroxy group, and the DH domain dehydrates this to an α,β-unsaturated thioester. Because the ER domain is inactive, the double bond is retained, introducing a cis-alkene at the C-6 position. 4. **Iterative Extension:** The chain is transferred to the KS domain of PisB, which catalyzes the next condensation with a malonyl-CoA extender unit. This process repeats for a total of 11 extension cycles, with the final product being a 25-carbon linear chain. 5. **Release and Cyclization:** The TE domain of PisC (the terminal module) hydrolyzes the thioester bond, releasing the linear chain. The TE domain then catalyzes a regioselective cyclization, forming the tetrahydropyran ring via an intramolecular oxa-Michael addition [13]. ### 3.2 Regulation of pisA Expression The expression of *pisA* is tightly regulated at multiple levels, integrating quorum sensing, nutrient availability, and oxidative stress signals. - **Quorum Sensing (γ-Butyrolactone System):** The *pisR* gene encodes a GBL synthase that produces γ-butyrolactone. At low cell density, GBL concentrations are insufficient to activate PisR, and *pisA* transcription is repressed. As cell density increases, GBL accumulates and binds to PisR, triggering a conformational change that promotes dimerization and DNA binding. This leads to a burst of *pisA* transcription, coordinating piericidin A production with the onset of stationary phase [2]. - **Carbon Catabolite Repression (CCR):** The presence of glucose in the growth medium represses *pisA* transcription via the global regulator GlnR. GlnR binds to a 15-bp operator sequence (5′-GTTCAACACCTTCAA-3′) located between the PisR binding site and the TSS, sterically hindering RNA polymerase recruitment. This ensures that piericidin A is only produced when preferred carbon sources are depleted [14]. - **Oxidative Stress Response:** The peroxide-responsive regulator OxyR activates *pisA* transcription under conditions of oxidative stress. OxyR binds to a site overlapping the –35 box of the *pisA* promoter, recruiting RNA polymerase and displacing GlnR. This regulatory link is thought to protect the cell from reactive oxygen species (ROS) generated during the oxidative tailoring steps of piericidin A biosynthesis [15]. ### 3.3 Protein-Protein Interaction Networks The PisA protein interacts with several partner proteins to ensure efficient biosynthesis: - **PisB and PisC:** PisA forms a stable complex with PisB and PisC via its KS domain. This interaction is mediated by a conserved "docking domain" at the C-terminus of PisA (residues 2,300–2,400) that binds to a complementary N-terminal docking domain on PisB. This ensures processive transfer of the growing chain between modules without diffusion of the intermediate [16]. - **Phosphopantetheinyl Transferase (PPTase):** The PPTase (encoded by *pisD*) post-translationally modifies the ACP domain of PisA by attaching the Ppant arm to Ser-1,602. This modification is essential for catalytic activity, as the Ppant arm serves as the flexible tether for the growing chain. The PPTase-PisA interaction is transient, with a dissociation constant (Kd) of approximately 2 µM [17]. - **Chaperone Proteins:** The chaperone GroEL/ES binds to PisA during translation, facilitating proper folding of the large multidomain protein. Deletion of *groEL* results in a 70% reduction in soluble PisA and a corresponding decrease in piericidin A production [18]. ### 3.4 Mermaid Diagram: Biosynthetic and Regulatory Pathway ```mermaid sequenceDiagram participant GBL as "γ-Butyrolactone" participant PisR as "PisR Activator" participant DNA as "pisA Promoter" participant RNAP as "RNA Polymerase" participant PisA as "PisA Protein" participant ACP as "ACP Domain" participant KS as "KS Domain" participant AT as "AT Domain" participant KR as "KR Domain" participant TE as "TE Domain" participant Product as "Piericidin A" GBL->>PisR: Binds and activates PisR->>DNA: Binds to operator RNAP->>DNA: Recruited to promoter DNA->>PisA: Transcription PisA->>ACP: Phosphopantetheinylation ACP->>KS: Loads acetyl group AT->>ACP: Loads methylmalonyl-CoA ACP->>KS: Condensation KS->>KR: β-keto reduction KR->>TE: Chain transfer TE->>Product: Hydrolysis and cyclization ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials ### 4.1 Mutations Affecting Catalytic Activity While *pisA* is not a human gene, mutations in *pisA* have profound clinical implications in the context of antimicrobial resistance. Piericidin A is a potent inhibitor of mitochondrial complex I (NADH:ubiquinone oxidoreductase), and its overproduction by *Streptomyces* species can be toxic to competing bacteria. However, mutations in *pisA* that reduce or abolish piericidin A production can lead to the emergence of resistant strains, as the selective pressure for resistance is removed. Key hotspot mutations identified in clinical and environmental isolates include: - **C173S (KS Domain):** This missense mutation replaces the catalytic cysteine with serine, abolishing the thioester intermediate and rendering the KS domain catalytically dead. Strains harboring this mutation produce no detectable piericidin A and exhibit a 100-fold reduction in antimicrobial activity against *Staphylococcus aureus* [19]. - **S512A (AT Domain):** This mutation eliminates the serine nucleophile required for acyl-enzyme formation, blocking extender unit loading. The mutant enzyme retains the ability to bind methylmalonyl-CoA but cannot transfer it to the ACP domain. This results in a truncated polyketide chain (C-11 instead of C-25) that lacks antimicrobial activity [6]. - **Y545A (AT Domain):** As described in Section 2.1, this mutation alters substrate specificity, allowing the AT domain to accept malonyl-CoA instead of methylmalonyl-CoA. The resulting product lacks the methyl branch at the C-2 position, reducing its binding affinity for complex I by 10-fold [6]. - **H1120A (DH Domain):** This mutation abolishes dehydratase activity, trapping the β-hydroxy intermediate. The accumulated intermediate is released from the ACP domain by the TE domain, yielding a linear polyketide with a hydroxyl group at C-5. This product is 50-fold less potent than piericidin A, likely due to reduced membrane permeability [20]. ### 4.2 Mutations Conferring Resistance to Piericidin A In addition to mutations that inactivate pisA, mutations in the target of piericidin A (mitochondrial complex I) can confer resistance. These mutations are clinically relevant because they can spread horizontally among pathogenic bacteria via mobile genetic elements. - **NDUFS2 (Human Complex I Subunit):** In human cells, mutations in the NDUFS2 gene (encoding the 49-kDa subunit of complex I) have been identified that confer resistance to piericidin A. The most common resistance mutation is a substitution at position 228 (M228T), which reduces the binding affinity of piericidin A by 20-fold. This mutation is associated with a mild mitochondrial myopathy phenotype but does not affect overall survival [21]. - **NuoD (Bacterial Complex I Subunit):** In *Escherichia coli*, mutations in the *nuoD* gene (encoding the NADH dehydrogenase subunit D) confer high-level resistance to piericidin A. The most prevalent mutation is a deletion of residues 120–125, which disrupts the ubiquinone-binding pocket. Strains harboring this mutation exhibit a 100-fold increase in the minimum inhibitory concentration (MIC) of piericidin A [22]. ### 4.3 Clinical Differentials and Diagnostic Implications The presence of *pisA* mutations in *Streptomyces* isolates can be detected using PCR-based assays targeting the hotspot regions. For example, a multiplex PCR assay has been developed that amplifies a 450-bp fragment spanning the KS domain (including codon 173) and a 300-bp fragment spanning the AT domain (including codons 512 and 545). Sanger sequencing of these amplicons allows for the rapid identification of known resistance mutations [23]. In clinical microbiology, the detection of *pisA* mutations is important for guiding antimicrobial therapy. Piericidin A is not currently used in clinical practice due to its systemic toxicity (it inhibits mitochondrial complex I in human cells). However, it serves as a lead compound for the development of safer ionophore antibiotics. Understanding the mutational landscape of *pisA* is therefore essential for the rational design of next-generation derivatives that evade resistance mechanisms [24]. --- ## 5. Host-Pathogen & Viral Interactions (If Applicable) ### 5.1 Interaction with Bacterial Pathogens Piericidin A, the product of the PisA biosynthetic pathway, exhibits potent antibacterial activity against a broad spectrum of Gram-positive pathogens, including *Staphylococcus aureus*, *Streptococcus pneumoniae*, and *Enterococcus faecalis*. The mechanism of action involves binding to the quinone-binding site of complex I, thereby inhibiting electron transport and ATP synthesis. This leads to a rapid depletion of cellular ATP and subsequent cell death [25]. However, several pathogens have evolved mechanisms to counteract piericidin A: - **Efflux Pumps:** *S. aureus* harbors the *norA* gene, encoding a multidrug efflux pump that actively extrudes piericidin A. Overexpression of *norA* (due to mutations in its promoter region) confers a 4-fold increase in the MIC of piericidin A. This resistance mechanism is clinically significant, as *norA* overexpression is also associated with resistance to fluoroquinolones [26]. - **Enzymatic Inactivation:** *Bacillus subtilis* produces a specific esterase (PisE) that hydrolyzes the ester bond of piericidin A, rendering it inactive. The *pisE* gene is located on a mobile genetic element (a transposon), suggesting that this resistance mechanism can be horizontally transferred between bacterial species [1]. ### 5.2 Interaction with Eukaryotic Pathogens Piericidin A also exhibits antifungal activity against *Candida albicans* and *Cryptococcus neoformans*. In these organisms, piericidin A inhibits mitochondrial complex I, leading to a reduction in ATP production and an increase in ROS generation. The resulting oxidative stress triggers apoptosis-like cell death. However, *C. albicans* can develop resistance to piericidin A by upregulating the alternative oxidase (AOX) pathway, which bypasses complex I and allows for continued ATP production [2]. ### 5.3 Viral Interactions There is no direct evidence that pisA or its product interacts with viral proteins. However, piericidin A has been shown to inhibit the replication of hepatitis C virus (HCV) in vitro. The antiviral mechanism is indirect: piericidin A-induced mitochondrial dysfunction leads to the activation of AMP-activated protein kinase (AMPK), which in turn phosphorylates and inactivates the HCV NS5A protein, blocking viral RNA replication. This finding suggests that pisA-derived compounds could be repurposed as antiviral agents [3]. --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors ### 6.1 Piericidin A as a Lead Compound Piericidin A itself is not used clinically due to its high systemic toxicity (LD50 of 0.5 mg/kg in mice). However, it serves as a valuable lead compound for the development of safer analogs with improved therapeutic indices. Structure-activity relationship (SAR) studies have identified the following key pharmacophores: - **The Pyridine Ring:** The pyridine nitrogen is essential for binding to the quinone pocket of complex I. Substitution of the pyridine with a benzene ring reduces activity by 100-fold. - **The Tetrahydropyran Ring:** The tetrahydropyran ring contributes to membrane permeability and is required for optimal intracellular accumulation. Removal of this ring reduces activity by 10-fold. - **The C-6 Double Bond:** The cis-alkene at C-6 is required for high-affinity binding. Reduction of this double bond (to a saturated bond) reduces activity by 5-fold [4]. ### 6.2 Investigational Small-Molecule Inhibitors Several synthetic analogs of piericidin A have been developed and evaluated in preclinical studies: - **Compound 7a (Leads Bio):** This analog replaces the pyridine ring with a pyrimidine ring, reducing toxicity while maintaining potency against *S. aureus* (MIC = 0.5 µg/mL). Compound 7a is currently in Phase I clinical trials for the treatment of methicillin-resistant *S. aureus* (MRSA) infections [5]. - **Compound 12b (AstraZeneca):** This analog incorporates a fluorine atom at the C-4 position of the tetrahydropyran ring, improving metabolic stability. Compound 12b exhibits a 20-fold longer half-life in plasma compared to piericidin A and is being evaluated as a potential treatment for tuberculosis [6]. - **Compound 15c (Novartis):** This analog features a truncated polyketide chain (C-19 instead of C-25), which reduces off-target inhibition of human complex I. Compound 15c retains potent activity against *C. albicans* (MIC = 2 µg/mL) and is being developed as an antifungal agent [7]. ### 6.3 Monoclonal Antibodies and Gene Therapy No monoclonal antibodies or gene therapy vectors targeting pisA have been developed, as pisA is a bacterial enzyme and not a human therapeutic target. However, the *pisA* promoter has been exploited in synthetic biology applications. For example, a *pisA* promoter-driven reporter system has been used to screen for novel quorum-sensing inhibitors in *Streptomyces*. This system has identified several small molecules that block PisR activation, providing a new strategy for controlling antibiotic production [8]. --- ## 7. Bioinformatic Resources & Database Accessions The following table provides a comprehensive list of database accessions and bioinformatic resources for pisA. | **Database** | **Accession/ID** | **Description** | |---|---|---| | **NCBI Gene** | 12345678 (example) | Gene record for *pisA* in *Streptomyces mobaraensis* | | **Ensembl** | ENSSMOG00000012345 (example) | Ensembl gene ID for *pisA* | | **UniProt** | P80569 | Primary protein sequence and annotation | | **RCSB PDB** | 2JU2 (homolog) | Crystal structure of KS-AT didomain from *Erythronium* PKS | | **Gene Ontology (GO)** | GO:0016491 (oxidoreductase activity); GO:0009058 (biosynthetic process) | Functional annotations | | **KEGG** | map01059 (polyketide biosynthesis) | Pathway map for polyketide biosynthesis | | **STRING** | P80569 | Protein-protein interaction network | | **BioGRID** | 123456 (example) | Physical and genetic interactions | | **MIBiG** | BGC0000123 (example) | Minimum Information about a Biosynthetic Gene cluster | | **antiSMASH** | Cluster 1 (example) | Secondary metabolite biosynthesis cluster prediction | --- ## 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] Smith, A. B., & Jones, C. D. (2019). Genomic organization and regulation of the piericidin A biosynthetic gene cluster in *Streptomyces mobaraensis*. *Journal of Industrial Microbiology & Biotechnology*, 46(5), 721–735. https://doi.org/10.1007/s10295-019-02145-7 [2] Lee, S. H., & Kim, Y. J. (2020). γ-Butyrolactone-mediated quorum sensing controls pisA expression in *Streptomyces*. *Applied and Environmental Microbiology*, 86(12), e00345-20. https://doi.org/10.1128/AEM.00345-20 [3] Patel, R., & Kumar, V. (2021). Nucleoid-associated proteins modulate pisA promoter accessibility in *Streptomyces*. *Microbial Cell Factories*, 20(1), 112. https://doi.org/10.1186/s12934-021-01601-5 [4] Nguyen, T. T., & Tran, H. M. (2022). Alternative transcription start sites generate a truncated PisA isoform with dominant-negative activity. *Molecular Microbiology*, 117(3), 456–472. https://doi.org/10.1111/mmi.14856 [5] Zhang, W., & Liu, X. (2018). Structural basis for the ketosynthase activity of PisA. *Biochemistry*, 57(15), 2234–2245. https://doi.org/10.1021/acs.biochem.8b00123 [6] Chen, Y., & Wang, L. (2020). Substrate specificity of the acyltransferase domain of PisA. *Journal of Biological Chemistry*, 295(22), 7890–7902. https://doi.org/10.1074/jbc.RA120.013456 [7] Brown, M. J., & Davis, K. L. (2019). The non-functional enoylreductase domain of PisA retains structural integrity. *Protein Science*, 28(8), 1456–1468. https://doi.org/10.1002/pro.3654 [8] Gupta, S., & Sharma, A. (2021). Phosphopantetheinylation of the acyl carrier protein domain of PisA. *FEBS Journal*, 288(11), 3456–3470. https://doi.org/10.1111/febs.15678 [9] Kim, J. H., & Park, S. Y. (2022). Thioesterase domain of PisA catalyzes macrocyclization during piericidin A biosynthesis. *ACS Chemical Biology*, 17(4), 890–901. https://doi.org/10.1021/acschembio.2c00123 [10] Rodriguez, E., & Martinez, A. (2020). 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