Arabinose Operon: Regulation and Mechanism Explained

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Introduction to the Arabinose Operon

The arabinose operon (often designated araBAD or the ara operon) is a classic inducible genetic system in Escherichia coli that governs the catabolism of L-arabinose, a five-carbon sugar. When L-arabinose is present in the environment and glucose is absent, E. coli transcribes three genes—araB, araA, and araD—whose protein products convert arabinose into D-xylulose-5-phosphate, an intermediate that enters the pentose phosphate pathway for energy production and biosynthesis.

The operon is a cornerstone of molecular biology instruction because it integrates two distinct layers of transcriptional control: a specific regulatory protein (AraC) that responds to arabinose, and a global regulatory system (catabolite repression via CAP-cAMP) that responds to glucose availability. Unlike the Lac Operon, which is primarily under negative control with a weak positive component, the arabinose operon is governed by a dual-function regulator that acts as both a repressor and an activator depending on ligand binding. This makes it an ideal model for understanding how bacteria integrate metabolic signals to make finely tuned gene expression decisions.

The arabinose system was first characterized genetically in the 1960s by Ellis Englesberg and colleagues, who identified the regulatory gene araC and demonstrated that it exerts both positive and negative control—a finding that was initially controversial because it challenged the then-prevailing view that regulators were either pure activators or pure repressors. Subsequent biochemical work, particularly from the laboratories of Robert Schleif and Gary Wilcox, revealed the molecular details of DNA looping, ligand-induced conformational changes, and cooperative protein-protein interactions that underlie the switch.

Structure of the Arabinose Operon

The arabinose operon is located at approximately 1.4 minutes on the E. coli chromosome (around 65,000 base pairs from the origin of replication). Its genetic organization is compact but intricate, with regulatory elements positioned both upstream and downstream of the structural genes.

Genes and Their Functions

The operon contains three structural genes transcribed as a single polycistronic mRNA:

• araB (ribulokinase): Encodes ribulokinase, which phosphorylates L-ribulose at the C5 position using ATP, producing L-ribulose-5-phosphate. The enzyme has a molecular weight of approximately 60 kDa per subunit and functions as a dimer.
• araA (L-arabinose isomerase): Encodes L-arabinose isomerase, which converts L-arabinose to L-ribulose. This enzyme is a hexamer with a subunit molecular weight of about 55 kDa and requires a divalent metal ion (typically Mn²⁺) for activity.
• araD (L-ribulose-5-phosphate 4-epimerase): Encodes L-ribulose-5-phosphate 4-epimerase, which epimerizes L-ribulose-5-phosphate to D-xylulose-5-phosphate. This enzyme is a homotetramer with a subunit weight of approximately 23 kDa.

The three enzymes act sequentially: AraA isomerizes arabinose to ribulose, AraB phosphorylates ribulose, and AraD epimerizes the phosphorylated intermediate. The pathway is inducible—basal expression is extremely low in the absence of arabinose—and the three genes are coordinately regulated because they share a single promoter.

Upstream of araB lies the regulatory gene araC, which is transcribed divergently from its own promoter (Pc). AraC is a 292-amino-acid protein (~33 kDa) that functions as a homodimer. Each monomer contains two distinct DNA-binding domains: an N-terminal domain that recognizes the araI and araO₂ sites, and a C-terminal domain that recognizes the araO₁ site. This dual-domain architecture is essential for the protein's ability to form DNA loops and switch between repressive and activating states.

Regulatory DNA Elements

The regulatory region of the arabinose operon spans roughly 300 base pairs between the araC gene and the araB structural gene. It contains three key protein-binding sites:

The araI region is the critical control point. It contains two AraC binding half-sites, designated I₁ (proximal, closer to the promoter) and I₂ (distal), arranged as direct repeats. Between these half-sites lies a binding site for the catabolite activator protein (CAP), which is required for full activation. The araO₂ site is located approximately 210 base pairs upstream of araI, and the intervening DNA can loop out when AraC binds simultaneously to both sites.

The promoter for the structural genes, P_BAD, is a σ⁷⁰-dependent promoter with a −10 sequence (TACTGT) and a −35 sequence (TTTACG) that deviate significantly from the consensus. This weak promoter requires both AraC and CAP for efficient transcription initiation. The promoter for araC itself, Pc, is relatively strong but is autoregulated by AraC binding to araO₁.

Regulatory Proteins: AraC and CAP

AraC: Dual Function

AraC is a remarkable regulatory protein because it can function as either a repressor or an activator depending on the presence of arabinose. This is achieved through ligand-induced conformational changes that alter the protein's DNA-binding geometry.

In the absence of arabinose, AraC exists predominantly as a dimer in which the N-terminal domain of one monomer binds to araO₂ while the C-terminal domain of the other monomer binds to araI (specifically the I₁ half-site). This arrangement creates a DNA loop of approximately 210 base pairs. The looping brings the araO₂-bound AraC monomer into proximity with the RNA polymerase binding site at P_BAD, sterically hindering polymerase access and maintaining the operon in a repressed state. The repression is not absolute—there is a low basal level of transcription—but it is sufficient to prevent wasteful enzyme synthesis in the absence of substrate.

When arabinose binds to AraC, it induces a conformational change in the N-terminal domain. Arabinose binds in a pocket formed by the N-terminal arm and the dimerization domain, with a dissociation constant (K_d) of approximately 1–5 mM for the isolated domain, though the effective in vivo concentration threshold is lower due to cooperative effects. Ligand binding causes a reorientation of the two domains within each monomer, such that the N-terminal domain can no longer bind araO₂ with high affinity. Instead, both monomers' N-terminal domains now bind to the two half-sites of araI (I₁ and I₂). This releases the DNA loop and positions AraC as a dimer adjacent to the promoter, where it can interact with RNA polymerase and CAP to stimulate transcription.

The switch between repression and activation is thus a classic example of an allosteric regulatory mechanism: the ligand (arabinose) acts as an inducer by shifting the equilibrium between two alternative DNA-binding conformations.

CAP-cAMP Complex

The catabolite activator protein (CAP, also known as CRP for cAMP receptor protein) is a global regulatory protein that mediates catabolite repression in E. coli. CAP is a homodimer of 209-amino-acid subunits (~23.6 kDa each) that binds to specific DNA sequences in the promoters of many catabolic operons, including the arabinose operon, the Lactose Operon, and the galactose operon.

CAP's DNA-binding activity depends on its association with cyclic AMP (cAMP). When glucose is scarce, the enzyme adenylate cyclase is activated, leading to increased intracellular cAMP concentrations. cAMP binds to CAP with a K_d of approximately 10–20 µM, inducing a conformational change that increases CAP's affinity for its DNA recognition site. The CAP-cAMP complex binds to a 22-base-pair consensus sequence (5'-TGTGA-N₆-TCACA-3') located upstream of the promoter.

In the arabinose operon, the CAP site is positioned between the I₁ and I₂ half-sites of araI, centered at approximately −78 relative to the P_BAD transcription start site. CAP binding bends the DNA by approximately 90°, which facilitates the interaction between AraC bound at I₁ and I₂ and helps recruit RNA polymerase to the weak P_BAD promoter. CAP makes direct protein-protein contacts with both AraC and the C-terminal domain of the RNA polymerase α subunit, stabilizing the formation of the transcription initiation complex.

The requirement for CAP explains why the arabinose operon is subject to catabolite repression: even when arabinose is abundant, if glucose is also present, cAMP levels remain low, CAP cannot bind, and transcription from P_BAD is severely reduced.

Mechanism of Regulation: The Arabinose Switch

The arabinose operon is regulated by a sophisticated switch that integrates two signals: arabinose availability (specific induction) and glucose availability (global catabolite repression). The system operates through three distinct states: repressed (no arabinose), induced (arabinose present, glucose absent), and catabolite-repressed (both arabinose and glucose present).

Repression State: DNA Looping

In the absence of arabinose, AraC maintains the operon in a repressed state through a DNA looping mechanism. The process can be broken down into discrete steps:

1. Dimerization: Two AraC monomers associate to form a dimer. The dimerization interface is located in the N-terminal domain, which also contains the arabinose-binding pocket.

1. Dual-site binding: In the apo (ligand-free) conformation, the AraC dimer binds simultaneously to araO₂ (via the N-terminal domain of one monomer) and to the I₁ half-site of araI (via the C-terminal domain of the other monomer). This is the energetically favored state because the protein's two DNA-binding domains are oriented such that they can span the 210-base-pair distance between these sites.

1. Loop formation: The intervening DNA between araO₂ and araI forms a loop. This loop is stabilized by the protein-protein interactions within the AraC dimer and by the intrinsic flexibility of the DNA.

1. Promoter occlusion: The looping brings the AraC dimer into a position where it physically interferes with RNA polymerase binding at P_BAD. The precise mechanism involves steric hindrance—the AraC-DNA complex occupies space that would be needed for polymerase to form a stable closed complex at the promoter.

The looping repression is highly efficient. In vivo measurements using reporter gene fusions indicate that the repressed level of P_BAD transcription is approximately 10- to 50-fold lower than the fully induced level. Importantly, the loop is not a static structure; it is in dynamic equilibrium with the unlooped state, and the equilibrium is shifted strongly toward the looped conformation in the absence of arabinose.

Activation State: Promoter Engagement

When arabinose is present, the switch flips. The sequence of events is as follows:

1. Arabinose binding: L-arabinose diffuses into the cell (facilitated by the arabinose transporter AraE and the low-affinity transporter AraFGH) and binds to the N-terminal domain of each AraC monomer. The binding is cooperative, with a Hill coefficient of approximately 1.5–2, meaning that binding to one monomer increases the affinity of the other.

1. Conformational change: Arabinose binding induces a rotation of the N-terminal domain relative to the C-terminal domain within each monomer. This reorientation changes the relative positions of the two DNA-binding domains in the dimer, making it sterically impossible for the N-terminal domain to bind araO₂ while the C-terminal domain binds araI.

1. Release of the loop: The AraC dimer dissociates from araO₂ and rebinds with both N-terminal domains to the I₁ and I₂ half-sites of araI. The DNA loop is released, and the promoter becomes accessible.

1. CAP binding: If glucose is absent, cAMP levels are high, and CAP-cAMP binds to its site between I₁ and I₂. CAP binding bends the DNA and makes direct contacts with AraC.

1. RNA polymerase recruitment: The AraC dimer at araI and CAP together recruit RNA polymerase to P_BAD. AraC contacts the C-terminal domain of the RNA polymerase α subunit, while CAP contacts both the α subunit and, in some configurations, the σ⁷⁰ subunit. These protein-protein interactions stabilize the closed complex and facilitate promoter melting and open complex formation.

1. Transcription initiation: Once the open complex is formed, RNA polymerase escapes the promoter and transcribes the araBAD genes. The mRNA is translated to produce the three catabolic enzymes.

The activation is highly synergistic: neither AraC alone nor CAP alone is sufficient for significant transcription from P_BAD. Both activators must be present and bound to their respective sites for efficient initiation. This dual requirement ensures that the operon is expressed only when both conditions are met: arabinose is available (AraC is in the activating conformation) and glucose is absent (CAP is active).

Catabolite Repression and Glucose Effect

cAMP-CAP Signaling

Catabolite repression is a global regulatory mechanism that ensures bacteria preferentially utilize glucose when it is available, even if other carbon sources are present. The arabinose operon is subject to this regulation through the cAMP-CAP system.

The signaling pathway operates as follows:

1. Glucose transport: When glucose is transported into the cell via the phosphotransferase system (PTS), the transport process itself leads to dephosphorylation of the PTS protein IIA^Glc.

1. Adenylate cyclase inhibition: The dephosphorylated IIA^Glc inhibits adenylate cyclase, the enzyme that synthesizes cAMP from ATP. Consequently, high glucose transport activity leads to low intracellular cAMP concentrations.

1. CAP inactivation: Without sufficient cAMP, CAP cannot bind to its DNA recognition sites. The apo-CAP protein has very low affinity for DNA and does not activate transcription.

1. Loss of cooperative activation: In the arabinose operon, the absence of CAP-cAMP at the araI site means that AraC alone cannot efficiently recruit RNA polymerase to P_BAD. The weak promoter (with its non-consensus −10 and −35 sequences) requires the combined action of both activators.

The result is that even in the presence of arabinose, the operon is transcribed at only 5–10% of the fully induced level when glucose is also present. This is a classic example of hierarchical carbon source utilization.

Diauxic Growth

The physiological consequence of catabolite repression is diauxic growth, a phenomenon first described by Jacques Monod. When E. coli is grown in a medium containing both glucose and arabinose, the bacteria first consume glucose, during which the arabinose operon remains repressed. Only after glucose is exhausted does a lag phase occur, during which the bacteria synthesize the arabinose catabolic enzymes. Following this lag, growth resumes on arabinose.

The diauxic lag represents the time required for the cell to switch its metabolic machinery from glucose to arabinose utilization. This includes the degradation of existing cAMP-phosphodiesterase products, the reactivation of adenylate cyclase, the synthesis of cAMP, the activation of CAP, and the subsequent induction of the arabinose operon. The entire process typically takes 20–40 minutes under standard laboratory conditions (LB or minimal medium at 37°C).

This regulatory logic is shared with the Lac Operon, which is also subject to catabolite repression. However, the arabinose operon differs in that its specific regulator (AraC) is a dual-function protein, whereas LacI is a pure repressor.

Experimental Methods Used to Study the Operon

The arabinose operon has been dissected using a wide array of molecular biology techniques. Understanding these methods is essential for appreciating how the current model was established.

DNA-Protein Interaction Assays

DNase I footprinting was instrumental in mapping the precise binding sites of AraC and CAP. In a typical footprinting experiment, a DNA fragment containing the regulatory region is end-labeled with ³²P at one end, incubated with purified AraC or CAP protein, and then partially digested with DNase I. The digestion products are separated on a denaturing polyacrylamide gel, and regions protected by protein binding appear as gaps (footprints) in the ladder of bands. This technique revealed the exact boundaries of araI, araO₁, and araO₂ and demonstrated that AraC protects distinct regions depending on whether arabinose is present.

Electrophoretic mobility shift assays (EMSAs) provided complementary information about binding affinity and stoichiometry. In an EMSA, a labeled DNA fragment is incubated with increasing concentrations of protein, and the mixture is run on a native polyacrylamide gel. Protein-DNA complexes migrate more slowly than free DNA, allowing visualization of complex formation. EMSAs with mutant DNA fragments and truncated proteins were used to determine the relative affinities of AraC for its various binding sites and to demonstrate that arabinose reduces AraC's affinity for araO₂ while increasing its affinity for araI.

DNA looping assays using electron microscopy directly visualized the looped DNA structures formed by AraC in the absence of arabinose. These experiments showed that the loop is approximately 210 base pairs in length and that loop formation requires both araO₂ and araI.

Reporter Systems

Reporter gene fusions have been used extensively to quantify promoter activity under different conditions. The most common approach fuses the P_BAD promoter to lacZ, encoding β-galactosidase, or to gfp, encoding green fluorescent protein. The activity of the promoter can then be measured by enzymatic assay (for LacZ, using the chromogenic substrate ONPG, 2-nitrophenyl-β-D-galactopyranoside) or by fluorescence intensity.

These reporter systems have been used to measure:

• The basal (uninduced) level of P_BAD activity
• The fully induced level (typically 10- to 50-fold higher than basal)
• The effect of mutations in the regulatory elements
• The kinetics of induction and repression

Site-directed mutagenesis of the regulatory elements has been crucial for dissecting the roles of individual base pairs. For example, mutations in the I₁ or I₂ half-sites that reduce AraC binding eliminate activation, while mutations in araO₂ that reduce AraC binding eliminate repression and lead to elevated basal expression. These experiments established that araO₂ is required for repression but not for activation, and that araI is required for activation but not for repression.

In vitro transcription assays using purified components (RNA polymerase, AraC, CAP, cAMP, and template DNA) demonstrated that both AraC and CAP are required for efficient transcription from P_BAD. These assays typically use a buffer containing 40 mM Tris-HCl (pH 8.0), 100 mM KCl, 10 mM MgCl₂, and 1 mM DTT, with reactions incubated at 37°C for 10–15 minutes before analysis by gel electrophoresis.

Common Misconceptions and Pitfalls

Students frequently encounter several conceptual difficulties when studying the arabinose operon. Addressing these directly will help consolidate understanding.

AraC as Pure Repressor or Activator

The most common error is to classify AraC as either a repressor or an activator. AraC is both, depending on the presence of arabinose. In the absence of arabinose, it represses P_BAD through DNA looping. In the presence of arabinose, it activates P_BAD by binding to araI and recruiting RNA polymerase. This is fundamentally different from LacI, which is a pure repressor that simply dissociates from the operator upon induction. The arabinose system is better compared to the Trp Operon in terms of having a dual-function regulator, though TrpR is a pure repressor and the tryptophan operon's activation is mediated by a different mechanism (attenuation).

Overlooking Catabolite Repression

A second common error is to describe the arabinose operon as being "on" whenever arabinose is present. This ignores the critical role of CAP. The operon is fully induced only when arabinose is present AND glucose is absent. In the presence of both sugars, the operon is only weakly transcribed. Students should remember that the arabinose operon is a two-input AND gate: both conditions must be satisfied for high-level expression.

Misunderstanding the Looping Mechanism

Students often struggle with the geometry of DNA looping. The key point is that AraC is a dimer, and in the repressed state, one monomer binds araO₂ while the other binds araI. This is only possible because the two DNA-binding domains of the dimer are oriented such that they can span the 210-base-pair distance. Arabinose binding changes the relative orientation of the domains, making it impossible to bind both sites simultaneously. The loop is not simply "released" by arabinose; rather, the conformational change in AraC makes the looped state energetically unfavorable, shifting the equilibrium toward the unlooped, activating state.

Confusing the Regulatory Elements

Students frequently mix up araO₁ and araO₂. Remember: araO₁ is involved primarily in autoregulation of the araC gene itself (repressing Pc), while araO₂ is involved in repression of P_BAD through DNA looping. They are not redundant operators.

Assuming the Operon Is Identical to the Lac Operon

While the arabinose and lac operons share the feature of catabolite repression, their specific regulatory mechanisms differ substantially. The Lac Operon uses a pure repressor (LacI) that is inactivated by allolactose, and its activator (CAP) is required for full induction but the promoter can function at a low level without it. The arabinose operon uses a dual-function regulator (AraC) and has a promoter that is essentially nonfunctional without both AraC and CAP. Additionally, the lac operon does not use DNA looping for repression (though it does have auxiliary operators), whereas looping is central to arabinose operon repression.

Practical Summary and Study Tips

Key Takeaways

• The arabinose operon (araBAD) encodes three enzymes that convert L-arabinose to D-xylulose-5-phosphate for entry into the pentose phosphate pathway.
• The operon is regulated by AraC, a dual-function protein that represses transcription in the absence of arabinose and activates it in the presence of arabinose.
• Repression is achieved through DNA looping: AraC binds simultaneously to araO₂ and araI, looping out the intervening DNA and blocking RNA polymerase access to P_BAD.
• Arabinose binding induces a conformational change in AraC that releases the loop and promotes binding to the two half-sites of araI, where AraC acts as an activator.
• Full activation requires CAP-cAMP, which binds to a site within araI and cooperatively recruits RNA polymerase. This makes the operon subject to catabolite repression: glucose presence reduces cAMP, preventing activation.
• The operon is a two-input AND gate: arabinose must be present (to activate AraC) and glucose must be absent (to activate CAP) for high-level transcription.
• The arabinose operon differs from the lac operon in its use of a dual-function regulator and its absolute requirement for CAP for significant transcription.

Exam Preparation Advice

1. Draw the system: Sketch the regulatory region with araO₂, araI (including I₁, I₂, and the CAP site), and P_BAD. Draw the AraC dimer in both the repressed (looped) and activated (unlooped) states. Label all protein-DNA and protein-protein interactions.

1. Compare and contrast: Create a table comparing the arabinose, Lac Operon, and Trp Operon. Include the regulatory protein, its mode of action, the inducer/corepressor, and the role of CAP.

1. Explain the logic: Practice explaining why the arabinose operon requires both AraC and CAP for activation. Understand that this is a "double-check" mechanism that ensures the cell only invests in arabinose catabolism when the substrate is available and glucose is not.

1. Know the terminology: Be comfortable with terms like cis-acting element, trans-acting factor, allostery, DNA looping, cooperativity, and catabolite repression. Use them precisely in your answers.

1. Work through the mechanism step by step: For an exam question asking you to "explain how the arabinose operon is regulated," structure your answer as: (a) the repressed state, (b) the induction process, (c) the role of CAP, and (d) the physiological significance.

Frequently Asked Questions

What is the arabinose operon?

The arabinose operon is a cluster of three genes (araB, araA, araD) in E. coli that encode enzymes for the catabolism of L-arabinose. Together with its regulatory gene araC and associated regulatory DNA elements, it forms a complete genetic switch that controls arabinose utilization. It is one of the best-studied model systems for understanding gene regulation in bacteria.

How does the arabinose operon work?

The operon is regulated by the AraC protein, which acts as a repressor in the absence of arabinose and an activator in its presence. In the repressed state, AraC forms a DNA loop between araO₂ and araI, blocking RNA polymerase access to the promoter. When arabinose binds AraC, the protein undergoes a conformational change that releases the loop and allows AraC to bind to araI as an activator. Full activation also requires the CAP-cAMP complex, which senses glucose availability.

What is the role of AraC in the arabinose operon?

AraC is a dual-function regulatory protein. In the absence of arabinose, it represses transcription by forming a DNA loop that blocks the promoter. In the presence of arabinose, it activates transcription by binding to the araI region and recruiting RNA polymerase. This dual function is made possible by the protein's two DNA-binding domains and its ability to undergo ligand-induced conformational changes.

Why is the arabinose operon important?

The arabinose operon is important for three reasons. First, it is a physiologically significant system for E. coli, allowing the bacterium to utilize arabinose as a carbon source. Second, it is a paradigm for understanding complex gene regulation, particularly the integration of specific and global regulatory signals. Third, it has practical applications: the P_BAD promoter is widely used in biotechnology for controlled protein expression, and the AraC-P_BAD system is a common tool for inducible gene expression in bacteria.

What is catabolite repression in the arabinose operon?

Catabolite repression refers to the downregulation of the arabinose operon when glucose is present. Glucose transport inhibits adenylate cyclase, reducing cAMP levels. Without cAMP, CAP cannot bind to its site in araI, and the operon cannot be fully activated even in the presence of arabinose. This ensures that the cell preferentially uses glucose, the most energetically favorable carbon source.

How does arabinose induce the operon?

Arabinose enters the cell through transporters (AraE and AraFGH) and binds to the N-terminal domain of AraC. This binding induces a conformational change that reorients the protein's two DNA-binding domains. The new conformation cannot bind araO₂ simultaneously with araI, so the DNA loop is released. AraC then binds to the I₁ and I₂ half-sites of araI, where it acts as an activator in cooperation with CAP-cAMP.

What is the difference between the arabinose and lac operons?

The arabinose and Lac Operon differ in several key respects. The lac operon uses a pure repressor (LacI) that is inactivated by allolactose, whereas the arabinose operon uses a dual-function regulator (AraC) that switches between repressor and activator conformations. The lac operon can achieve some transcription with CAP alone (though at reduced levels), while the arabinose operon requires both AraC and CAP for significant transcription. Additionally, the arabinose operon uses DNA looping as its primary repression mechanism, while the lac operon relies primarily on simple operator occlusion.

Key Takeaways

• The arabinose operon (araBAD) encodes three enzymes for L-arabinose catabolism and is regulated by the dual-function protein AraC.
• In the absence of arabinose, AraC represses transcription by forming a DNA loop between araO₂ and araI, blocking RNA polymerase access to P_BAD.
• Arabinose binding induces a conformational change in AraC, releasing the loop and converting AraC into an activator that binds the I₁ and I₂ half-sites of araI.
• Full activation requires CAP-cAMP, which binds within araI and cooperatively recruits RNA polymerase, making the operon subject to catabolite repression by glucose.
• The operon functions as a two-input AND gate: arabinose must be present and glucose must be absent for high-level expression.
• The arabinose operon differs from the lac operon in its use of a dual-function regulator, its absolute requirement for CAP, and its reliance on DNA looping for repression.
• Understanding the arabinose operon provides a foundation for grasping how bacteria integrate multiple environmental signals to make precise gene expression decisions.

Further Reading

• Schleif R. AraC protein, regulation of the l-arabinose operon in Escherichia coli, and the light switch mechanism of AraC action. FEMS microbiology reviews. 2010. PubMed 20491933
• Schleif R. Regulation of the L-arabinose operon of Escherichia coli. Trends in genetics : TIG. 2000. PubMed 1110270602153-3)
• Schleif R. A Career's Work, the l-Arabinose Operon: How It Functions and How We Learned It. EcoSal Plus. 2022. PubMed 36519894
• Schleif R. DNA looping and regulation of the arabinose operon. Harvey lectures. 1988. PubMed 3079279
• Schleif R. Induction of the L-arabinose operon. Journal of molecular biology. 1969. PubMed 490220990066-7)
• Arabinose operon in vitro. Nature. 1971. PubMed 16063353

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