Recombinant Uncharacterized ABC transporter ATP-binding protein Rv1272c/MT1310 (Rv1272c, MT1310)

What is Rv1272c/MT1310 and how is it classified?

Rv1272c (also known as MT1310) is a probable drugs-transport transmembrane ATP-binding protein ABC transporter in Mycobacterium tuberculosis H37Rv. It belongs to the ATP-binding transport protein family (ABC transporters), specifically the MSBA subfamily . The protein consists of 631 amino acids and contains characteristic motifs including PS00017 ATP/GTP-binding site motif A (P-loop) and PS00211 ABC transporters family signature . Structurally and functionally, it shares similarities with other bacterial ABC transporters, particularly those involved in fatty acid transport mechanisms.

What is the genomic location and orientation of Rv1272c?

Rv1272c is located in the Mycobacterium tuberculosis H37Rv genome at coordinates 1420410 to 1422305 on the negative strand . This positioning within the genome may provide insights into potential operonic structures or regulatory elements that influence its expression. Researchers investigating transcriptional regulation of this gene should note its orientation when designing promoter studies or analyzing upstream regulatory sequences.

What is the general function of ABC transporters in bacterial systems?

ABC transporters utilize ATP hydrolysis to drive the transport of various substrates across membranes. In bacterial systems, they typically function in nutrient uptake, export of toxins, and maintenance of membrane homeostasis . The mechanotransmission process employed by some ABC transporters like MacB involves coupling cytoplasmic ATP hydrolysis with transmembrane conformational changes to perform work in the extra-cytoplasmic space . In the case of Rv1272c, its primary function appears to be mediating the import of long-chain fatty acids, which may contribute to triacylglycerol synthesis and accumulation in M. tuberculosis .

How does Rv1272c differ from other characterized ABC transporters?

Unlike many ABC transporters involved in drug export, Rv1272c shows a primary function in fatty acid import . Recent research demonstrates that when expressed in E. coli, Rv1272c enhances the import of radiolabeled fatty acids and increases their metabolic incorporation into cardiolipin and phosphatidylglycerol . This functional characteristic distinguishes it from other mycobacterial ABC transporters previously studied. Additionally, Rv1272c shows sequence similarities with both bacterial ABC transporters that mediate fatty acid import for TAG synthesis and plant ABC transporters involved in fatty acid transport .

What is the significance of Rv1272c in M. tuberculosis dormancy and persistence?

Rv1272c likely plays a crucial role in M. tuberculosis dormancy and persistence by facilitating fatty acid import for triacylglycerol (TAG) accumulation . During dormancy, M. tuberculosis utilizes host-derived fatty acids to synthesize TAG as an energy reserve. The transport of these fatty acids from host cells is essential for dormancy-associated TAG synthesis, and Rv1272c appears to be one of the key transporters involved in this process . While non-essential for in vitro growth, Rv1272c is required for growth in mouse spleen according to transposon site hybridization (TraSH) experiments, suggesting its importance in host-pathogen interactions during infection .

How does the structure of Rv1272c relate to its function in fatty acid transport?

While the complete three-dimensional structure of Rv1272c has not been fully characterized, sequence analysis reveals it contains the ATP/GTP-binding site motif A (P-loop) and ABC transporters family signature . These structural features are critical for ATP binding and hydrolysis, providing the energy necessary for substrate transport. The transmembrane domains likely form a channel or pore through which fatty acids are transported. Research indicates that when expressed in E. coli, Rv1272c causes a significant increase in the metabolic incorporation of radiolabeled long-chain fatty acids into cardiolipin (a tetra-acylated phospholipid) and phosphatidylglycerol . This functional data suggests the protein contains specific binding sites or structural features that facilitate interaction with and transport of long-chain fatty acids across the membrane.

What transcriptional changes occur in Rv1272c expression under various stress conditions?

Transcriptomic studies have shown variable expression patterns for Rv1272c under different conditions. In a genomic and transcriptomic study of lineage-specific variation, Rv1272c showed differential expression between various M. tuberculosis strains . While specific fold-changes for Rv1272c were not directly provided in the search results, the gene's expression appears to be modulated under certain stress conditions relevant to the host environment. This suggests that transcriptional regulation of Rv1272c may be part of the adaptive response of M. tuberculosis to environmental stresses encountered during infection.

What is the role of Rv1272c in M. tuberculosis lipid metabolism and cell wall biosynthesis?

Rv1272c contributes significantly to M. tuberculosis lipid metabolism by facilitating the import of long-chain fatty acids . These imported fatty acids can be incorporated into various lipid components, including triacylglycerols for energy storage and complex lipids for cell wall biosynthesis. The functional categorization of Rv1272c as involved in "Cell wall and cell processes" further supports its role in maintaining cell envelope integrity . The protein's ability to enhance the metabolic incorporation of fatty acids into cardiolipin and phosphatidylglycerol when expressed in E. coli suggests it may play a similar role in mycobacterial membrane lipid biosynthesis .

What techniques are most effective for studying Rv1272c function in vitro?

Several complementary techniques are effective for studying Rv1272c function:

• Heterologous Expression Systems: Expressing Rv1272c in E. coli has proven effective for functional characterization, as demonstrated by studies showing enhanced fatty acid import in Rv1272c-expressing E. coli .

• Radiolabeled Substrate Transport Assays: Using radiolabeled fatty acids to track transport across membranes provides quantitative data on Rv1272c transport function .

• Lipid Incorporation Analysis: Measuring the metabolic incorporation of radiolabeled fatty acids into specific lipid classes (e.g., cardiolipin, phosphatidylglycerol) helps elucidate the downstream effects of Rv1272c-mediated transport .

• Proteomics Analysis: Mass spectrometry-based approaches have successfully identified Rv1272c in Triton X-114 extracts and membrane protein fractions of M. tuberculosis H37Rv .

• Mutagenesis Studies: Targeted mutations in ATP-binding motifs or transmembrane domains can help identify critical residues for Rv1272c function.

These methodologies provide complementary data on Rv1272c localization, substrate specificity, and transport kinetics.

How can researchers generate and purify recombinant Rv1272c protein for structural and functional studies?

The production of recombinant Rv1272c protein involves several steps:

• Expression System Selection: E. coli has been successfully used to express functional Rv1272c protein . Expression constructs typically include a His-tag for purification purposes .

• Optimization of Expression Conditions: Due to the membrane-associated nature of Rv1272c, expression conditions need optimization to prevent protein aggregation and ensure proper folding.

• Membrane Protein Extraction: Techniques using detergents like Triton X-114 have successfully extracted Rv1272c from membrane fractions .

• Affinity Purification: His-tagged Rv1272c can be purified using nickel affinity chromatography .

• Quality Control: Size exclusion chromatography and activity assays should be performed to ensure the purified protein is properly folded and functional.

The table below summarizes available recombinant Rv1272c protein options:

What are the appropriate controls and considerations for fatty acid transport assays with Rv1272c?

When conducting fatty acid transport assays with Rv1272c, researchers should implement the following controls and considerations:

• Negative Controls: Include cells expressing an empty vector or an unrelated membrane protein to differentiate between specific Rv1272c-mediated transport and passive diffusion or non-specific membrane effects.

• Positive Controls: Ideally, include a known fatty acid transporter with well-characterized kinetics for comparison.

• Substrate Specificity: Test various fatty acids with different chain lengths and saturation levels to determine Rv1272c substrate preference. Research has shown Rv1272c particularly affects long-chain fatty acid transport .

• ATP Dependence: Since Rv1272c is an ATP-binding cassette transporter, assays should include conditions with and without ATP to confirm the energy-dependent nature of transport.

• Competitive Inhibition: Include assays with unlabeled fatty acids to assess competitive inhibition of radiolabeled substrate transport.

• Time Course and Concentration Dependence: Perform assays at multiple time points and substrate concentrations to determine transport kinetics (Km and Vmax values).

• Temperature and pH Controls: Assess transport activity under various temperature and pH conditions to determine optimal parameters and physiological relevance.

These controls help ensure the specificity and reliability of transport data for Rv1272c characterization.

How can genetic knockout or knockdown approaches be used to study Rv1272c function in M. tuberculosis?

Several genetic approaches can be employed to study Rv1272c function in M. tuberculosis:

• Transposon Mutagenesis: Previous studies using Himar1 transposon mutagenesis have shown Rv1272c is non-essential for in vitro growth in H37Rv and CDC1551 strains but required for growth in mouse spleen . Researchers can use existing transposon mutant libraries or create new insertions.

• CRISPR Interference (CRISPRi): For conditional knockdown, CRISPRi can downregulate Rv1272c expression without complete deletion, allowing study of partial loss-of-function phenotypes.

• Regulated Expression Systems: Tetracycline-inducible or repressible systems allow controlled modulation of Rv1272c expression to study dose-dependent effects.

• Complementation Studies: After generating knockout strains, complementation with wild-type or mutated versions of Rv1272c can confirm phenotype specificity and identify critical functional domains.

• Phenotypic Analysis: Key phenotypes to assess include:

  • Growth kinetics in various media (especially lipid-limited conditions)

  • Lipid composition analysis by thin-layer chromatography and mass spectrometry

  • Fatty acid uptake using radiolabeled substrates

  • Survival under stress conditions (nutrient limitation, hypoxia, etc.)

  • Virulence in cellular and animal infection models

The TARGET website mentioned in the search results may have mutants available for researchers interested in Rv1272c functional studies.

What is the potential of Rv1272c as a drug target for tuberculosis treatment?

Rv1272c presents several characteristics that make it a promising drug target for tuberculosis treatment:

• Essential for In Vivo Growth: While non-essential for in vitro growth, Rv1272c is required for growth in mouse spleen according to TraSH experiments , suggesting its importance during infection.

• Role in Persistence: Its involvement in fatty acid import for TAG accumulation suggests Rv1272c may be critical for M. tuberculosis persistence and dormancy, which are major challenges in tuberculosis treatment.

• Unique Function: As an ABC transporter with a specialized role in fatty acid import , Rv1272c might offer selective targeting possibilities with limited cross-reactivity with human transporters.

• Membrane Accessibility: As a transmembrane protein , Rv1272c potentially presents binding sites that are accessible to small molecule inhibitors without needing to cross the mycobacterial cell wall.

• Druggable Protein Family: ABC transporters have proven druggable in other contexts, with successful development of inhibitors targeting their ATP-binding domains or substrate-binding regions.

Researchers developing inhibitors against Rv1272c should focus on compounds that specifically disrupt its fatty acid transport function or ATP hydrolysis activity, potentially impairing M. tuberculosis adaptation to the host environment.

How does Rv1272c contribute to M. tuberculosis virulence and pathogenesis?

Rv1272c appears to contribute to M. tuberculosis virulence through several mechanisms:

• Nutrient Acquisition: By facilitating fatty acid import , Rv1272c helps M. tuberculosis utilize host-derived lipids as carbon and energy sources during infection.

• TAG Accumulation: The imported fatty acids contribute to triacylglycerol synthesis and accumulation , which serves as an energy reserve during dormancy and persistence.

• In Vivo Survival: TraSH experiments have shown Rv1272c is required for growth in mouse spleen , indicating its importance in adapting to the host environment.

• Membrane Homeostasis: The integration of imported fatty acids into phospholipids like cardiolipin and phosphatidylglycerol may help maintain membrane integrity under host-imposed stress conditions.

• Potential Role in Drug Resistance: As an ABC transporter thought to be involved in active transport of drugs across the membrane , Rv1272c might also contribute to intrinsic drug resistance mechanisms in M. tuberculosis.

The functional category of Rv1272c as involved in "Cell wall and cell processes" further supports its role in maintaining cell envelope integrity, which is critical for mycobacterial virulence and resistance to host defense mechanisms.

Are there genetic variations in Rv1272c across clinical M. tuberculosis isolates, and what are their functional implications?

Genomic sequencing has identified an extensive repertoire of single nucleotide polymorphisms (SNPs) amongst clinical isolates of the Mycobacterium tuberculosis complex (MTBC) . While the search results don't provide specific data on Rv1272c variations, genomic and transcriptomic studies of lineage-specific variation suggest potential differences in gene expression or sequence across strains .

Possible functional implications of Rv1272c variations include:

• Altered Substrate Specificity: Mutations in substrate-binding regions could change the range of fatty acids transported.

• Transport Efficiency: Variations affecting ATP binding or hydrolysis might alter the rate or efficiency of fatty acid import.

• Expression Level Differences: Promoter or regulatory region variations could affect Rv1272c expression levels under different conditions.

• Strain-Specific Adaptations: Sequence variations might reflect adaptations to different host environments or transmission dynamics among geographic lineages.

• Drug Resistance Contributions: If Rv1272c contributes to drug efflux, variations could potentially affect susceptibility to certain antibiotics.

Researchers investigating clinical relevance should consider sequencing Rv1272c across diverse clinical isolates and correlating genetic variations with phenotypic differences in lipid metabolism, persistence, and virulence.

How might inhibition of Rv1272c affect M. tuberculosis dormancy and reactivation?

Inhibition of Rv1272c could significantly impact M. tuberculosis dormancy and reactivation through several mechanisms:

• Impaired TAG Accumulation: By blocking fatty acid import , Rv1272c inhibition would likely reduce the bacterium's ability to synthesize and accumulate triacylglycerol, which serves as an energy reserve during dormancy.

• Nutrient Limitation: Reduced access to host-derived fatty acids would limit available carbon and energy sources during infection, potentially compromising long-term survival.

• Altered Membrane Composition: Decreased incorporation of imported fatty acids into membrane phospholipids like cardiolipin and phosphatidylglycerol might affect membrane fluidity, integrity, and stress resistance.

• Metabolic Stress: Forcing M. tuberculosis to rely on de novo fatty acid synthesis rather than import could increase metabolic stress and potentially enhance susceptibility to other stresses.

• Reactivation Vulnerability: If dormant bacilli depend on stored TAG for reactivation, depleting these reserves through Rv1272c inhibition might hinder the transition from dormancy to active growth.

These effects make Rv1272c an interesting target for developing interventions against latent tuberculosis, potentially preventing establishment of dormancy or disrupting the dormant state to enhance clearance by host immunity or conventional antibiotics.