Recombinant UPF0098 protein Rv2140c/MT2198 (Rv2140c, MT2198)

What is Rv2140c and what is its genomic context in Mycobacterium tuberculosis?

Rv2140c (also known as TB18.6) is a conserved protein in Mycobacterium tuberculosis H37Rv classified as a phosphatidylethanolamine-binding protein (PEBP), homologous to Raf kinase inhibitor protein (RKIP) in humans . It is located at coordinates 2399798-2400328 on the negative strand of the M. tuberculosis genome . The protein consists of 176 amino acids and has been identified in multiple cellular compartments including the culture supernatant, membrane fraction, and whole cell lysates of M. tuberculosis H37Rv through various proteomics studies .

How conserved is Rv2140c across bacterial species?

Rv2140c shows significant evolutionary conservation across diverse bacterial genera. Sequence analysis reveals good similarity to hypothetical proteins from Streptomyces coelicolor (58% identity) and to the 17.1 kDa Escherichia coli protein YbhB (46.2% identity in 156 aa overlap) . This high degree of conservation suggests an evolutionarily important role despite not being essential for in vitro growth of M. tuberculosis, as demonstrated through multiple independent transposon mutagenesis studies .

What evidence exists for Rv2140c's role in phosphorylation regulation?

Quantitative phosphoproteomic analysis comparing recombinant M. smegmatis strains expressing Rv2140c (Ms_Rv2140c) versus vector control (Ms_vec) revealed that Rv2140c differentially regulates 425 phosphorylated sites representing 282 proteins . Gene ontology (GO) and cluster of orthologous groups (COG) analyses showed that Rv2140c-regulated phosphoproteins were primarily associated with metabolism and cellular processes . Specifically, Rv2140c significantly repressed phosphoproteins involved in signaling pathways, including serine/threonine-protein kinases and two-component systems .

How does Rv2140c affect cell wall properties in mycobacteria?

Experimental evidence indicates that Rv2140c significantly influences cell wall composition by upregulating phosphoproteins involved in the arabinogalactan biosynthesis pathway . Consistent with these phosphoproteomic data, heterologous expression of Rv2140c in M. smegmatis altered several phenotypic properties including:

These changes suggest Rv2140c plays a crucial role in modulating cell wall integrity and composition, potentially contributing to M. tuberculosis survival under stressful host conditions .

What approaches are recommended for recombinant expression and purification of Rv2140c?

Based on research methodologies described in the literature, a systematic approach for recombinant Rv2140c production would include:

• Gene cloning into a suitable expression vector

• Transformation into an appropriate expression host (E. coli or mycobacterial expression systems)

• Optimization of expression conditions (temperature, inducer concentration, duration)

• Cell lysis under conditions that preserve protein structure

• Initial purification via affinity chromatography (if tagged constructs are used)

• Secondary purification steps (ion exchange, size exclusion chromatography)

• Verification of purity by SDS-PAGE and functional activity assays

When designing expression constructs, researchers should consider that Rv2140c has been identified in the membrane fraction of M. tuberculosis, suggesting potential membrane association that may affect solubility and purification strategies .

How can researchers investigate the phosphoprotein regulatory activity of Rv2140c?

To study Rv2140c's phosphoregulatory functions, researchers have employed quantitative phosphoproteomics approaches . A recommended workflow includes:

• Generation of recombinant strains expressing Rv2140c (e.g., in M. smegmatis as a surrogate host)

• Growth of bacterial cultures under standardized conditions

• Protein extraction and phosphopeptide enrichment

• LC-MS/MS analysis for phosphopeptide identification

• Quantitative comparison between Rv2140c-expressing and control strains

• Bioinformatic analysis including GO and COG functional categorization

• Validation of key phosphorylation changes using targeted approaches

• Correlation of phosphoproteome changes with phenotypic outcomes

This approach has successfully identified hundreds of differentially regulated phosphorylation sites, providing insights into Rv2140c's regulatory network .

What phenotypic assays effectively evaluate Rv2140c's impact on bacterial physiology?

Based on published findings, researchers investigating Rv2140c's physiological effects should consider these assays:

These assays have revealed that Rv2140c expression alters colony morphology, cell wall permeability, acid resistance, and lactose transport in M. smegmatis, suggesting similar roles in M. tuberculosis .

How does Rv2140c compare functionally to Rv2145c in M. tuberculosis?

While focusing on distinct biological processes, both Rv2140c and Rv2145c contribute to M. tuberculosis adaptation and survival:

While Rv2140c primarily affects bacterial physiology through internal regulatory mechanisms, Rv2145c appears to function as a virulence factor by manipulating host immune responses .

What structural and functional similarities exist between bacterial Rv2140c and eukaryotic RKIP proteins?

Rv2140c belongs to the phosphatidylethanolamine-binding protein (PEBP) family, which includes human Raf kinase inhibitor protein (RKIP) . This evolutionary relationship suggests possible shared mechanisms despite divergent specific functions:

• Both proteins likely share core structural features characteristic of the PEBP family

• Both function as regulatory proteins affecting phosphorylation networks

• In humans, RKIP inhibits the Raf-MEK-ERK pathway, while Rv2140c regulates bacterial phosphoproteins

• Both may bind similar phospholipid ligands through conserved binding pockets

The homology between bacterial Rv2140c and human RKIP raises intriguing questions about potential molecular mimicry or convergent evolution of regulatory mechanisms across domains of life .

What are the methodological challenges in studying Rv2140c's precise mechanism of action?

Researchers face several technical obstacles when investigating Rv2140c:

• Complexity of phosphorylation networks - The protein affects hundreds of phosphorylation sites, making it challenging to distinguish direct from indirect effects

• Redundant regulatory pathways - As a non-essential gene, functional compensation may mask phenotypes in knockout studies

• Potential protein-lipid interactions - As a PEBP family member, studying its interactions with membrane components requires specialized techniques

• Limited structural information - Complete three-dimensional structure determination would aid mechanistic understanding

• Technical difficulties in mycobacterial genetics - Slow growth and challenging genetic manipulation of pathogenic mycobacteria

Addressing these challenges requires integrated approaches combining genetics, biochemistry, structural biology, and systems-level analyses.

How might Rv2140c contribute to M. tuberculosis pathogenesis despite being non-essential for in vitro growth?

Several lines of evidence suggest potential roles in pathogenesis:

• Presence in culture filtrate and membrane fractions indicates potential interaction with host environment

• Regulation of cell wall components (arabinogalactan) may affect bacterial resistance to host defenses

• Enhanced survival in acidic conditions when expressed in M. smegmatis suggests possible contribution to phagosomal survival

• Homology to human RKIP suggests potential for molecular mimicry or host-pathogen interaction

• Non-essentiality in vitro does not preclude importance during infection, particularly under specific stress conditions

Further research using infection models would be necessary to definitively establish Rv2140c's role in pathogenesis.

What research technologies would advance our understanding of Rv2140c's structural dynamics and interaction network?

Leading-edge approaches for deeper mechanistic insights include:

• Cryo-electron microscopy for high-resolution structural determination

• X-ray crystallography of Rv2140c alone and in complex with binding partners

• Hydrogen-deuterium exchange mass spectrometry to map dynamic regions

• Phospholipidomics to identify specific lipid binding preferences

• Proximity labeling techniques to identify interaction partners in living bacteria

• Time-resolved phosphoproteomics to determine the sequence of regulatory events

• Single-cell approaches to examine heterogeneity in Rv2140c function within bacterial populations

• Integrative multi-omics to position Rv2140c within regulatory networks

These technologies could reveal how Rv2140c selectively regulates specific phosphorylation pathways and contributes to mycobacterial adaptation.

What are promising avenues for further investigation of Rv2140c's biological significance?

Several research directions warrant exploration:

• Determination of high-resolution three-dimensional structure to understand phospholipid and protein binding mechanisms

• Identification of direct interaction partners and substrates through targeted approaches

• Generation of phospho-site specific antibodies to monitor Rv2140c-dependent regulation

• Investigation of Rv2140c expression and function during different stages of infection

• Comparative analysis of Rv2140c homologs across pathogenic and non-pathogenic mycobacteria

• Evaluation of potential cross-talk between Rv2140c and other regulatory systems in M. tuberculosis

• Assessment of Rv2140c's role in antibiotic tolerance and stress response

These investigations would provide deeper insights into how this conserved regulatory protein contributes to M. tuberculosis biology.

How might understanding Rv2140c inform tuberculosis treatment strategies?

While Rv2140c itself is non-essential for in vitro growth, its regulatory functions suggest several potential therapeutic applications:

• Targeting signaling networks regulated by Rv2140c might sensitize bacteria to existing antibiotics

• Understanding its role in cell wall modification could reveal new vulnerabilities in the mycobacterial envelope

• Inhibitors preventing Rv2140c-mediated acid adaptation might enhance bacterial clearance in phagosomes

• The protein's interaction network might reveal novel essential targets within its downstream pathways

• Structural insights could enable rational design of compounds targeting specific protein-protein or protein-lipid interactions

Such approaches could potentially address challenges in tuberculosis treatment including bacterial persistence and drug resistance.

How does research on Rv2140c complement studies of other M. tuberculosis proteins like Rv2145c?

Integrated analysis of multiple M. tuberculosis proteins provides a more comprehensive understanding of pathogenesis mechanisms:

• While Rv2140c modifies bacterial physiology through phosphoregulation , Rv2145c directly stimulates host IL-10 production and STAT3 activation

• Both proteins contribute to a favorable environment for bacterial survival but through distinct mechanisms

• Combined study of these proteins illustrates how M. tuberculosis employs both host-directed and bacterial-directed strategies

• Understanding potential interactions or synergy between these pathways could reveal new intervention points

• Comparative analysis helps prioritize targets for further research based on their roles in pathogenesis

This integrated perspective is essential for developing comprehensive models of M. tuberculosis virulence and adaptation.

What experimental systems best evaluate the functional significance of Rv2140c during infection?

Optimal experimental approaches would include:

• Macrophage infection models comparing wild-type and Rv2140c-deficient M. tuberculosis

• Animal infection studies using knockout, complemented, and overexpression strains

• Dual RNA-seq to simultaneously monitor host and pathogen transcriptional responses

• Time-course phosphoproteomic analysis during infection to track dynamic regulation

• Co-infection experiments to assess competitive fitness in vivo

• Tissue-specific analyses to examine Rv2140c's role in different microenvironments

• Systems biology integration of multiple data types (transcriptomics, proteomics, metabolomics)

These approaches would provide comprehensive insights into how Rv2140c functions during the complex process of host-pathogen interaction.