Generated using OpenAI Deep Research API
UniProt ID: O07238
Directory alias: Rv0311
The Rv0311 gene of Mycobacterium tuberculosis H37Rv encodes a conserved hypothetical protein of 409 amino acids with no assigned name (orca2.tamu.edu) (orca1.tamu.edu). To date, its precise molecular function remains unknown, as it lacks clear similarity to characterized proteins (no close homologs in PDB >35% identity) (orca2.tamu.edu). In silico analysis has revealed that Rv0311’s sequence contains a protein splicing signature motif (PROSITE PS00881), which is associated with inteins (self-splicing proteins) (mycobrowser.epfl.ch). This suggests Rv0311 may include an intein-like domain or autoproteolytic element, although no splicing activity has been experimentally confirmed. The presence of this motif and conserved catalytic residues (e.g. a histidine–aspartate–histidine–cysteine sequence) hints that Rv0311 could function as an enzyme or processing factor, potentially involved in post-translational protein modification or DNA/RNA metabolism (mycobrowser.epfl.ch). However, direct biochemical activity of Rv0311 has not been demonstrated, and it is currently annotated simply as a “hypothetical protein” with unknown function (orca2.tamu.edu). Notably, UniProt-based Gene Ontology (GO) annotations suggest a role in growth and pathogenesis, implying that while the exact mechanism is unclear, Rv0311 is believed to contribute to the bacterium’s proliferation and virulence (orca2.tamu.edu). These broad annotations are likely inferred from genetic studies (e.g. essentiality and infection models) rather than a known molecular mechanism. In summary, Rv0311 is an uncharacterized but conserved protein thought to be enzymatic in nature, potentially carrying an intein-like segment, and required for M. tuberculosis to grow and cause disease, even though its specific substrate or biochemical pathway remains to be discovered.
Multiple lines of evidence indicate that Rv0311 is associated with the cell envelope and is likely an exported/secreted protein. The N-terminal sequence of Rv0311 is hydrophobic and resembles a signal peptide, consistent with secretion via the Sec pathway. Proteomics studies have indeed identified the Rv0311 protein in culture supernatants and membrane fractions. For example, Rv0311 was detected by mass spectrometry in detergent-phase (Triton X-114) extracts of M. tuberculosis H37Rv (mycobrowser.epfl.ch). Triton X-114 extraction enriches for hydrophobic, membrane-associated proteins, suggesting Rv0311 either integrates into or peripherally associates with the cell membrane. In a comprehensive fractionation study, Rv0311 was also found in the culture filtrate, membrane protein fraction, and whole-cell lysate, confirming that a portion of the protein is exported outside the cell (culture filtrate) while some remains cell-associated (mycobrowser.epfl.ch). The presence of Rv0311 in the extracellular milieu implies it may function in the periplasmic space or cell wall interface, possibly interacting with host tissues or cell-wall components. Consistently, Rv0311 is categorized as a cell envelope-associated protein in the H37Rv genome annotations (mycobrowser.epfl.ch). It is not predicted to contain any large trans-membrane helices (orca2.tamu.edu), so if anchored, it could be via a post-translational modification. (Notably, despite a signal peptide, Rv0311’s sequence does not perfectly match the canonical lipoprotein “lipobox,” so it may be a non-lipidated secretory protein rather than a lipoprotein.) In summary, Rv0311 is likely located in the cell wall or extracellular space of M. tuberculosis, where it could contribute to cell envelope physiology or mediate interactions with the host environment.
Though its exact function is unknown, Rv0311 appears to play important roles in key biological processes of M. tuberculosis. Genetic and phenotypic data link this gene to bacterial growth, stress adaptation, and pathogenesis. Rv0311 is broadly conserved and has been placed in the category of “conserved hypotheticals,” many of which are crucial for core metabolism or survival (mycobrowser.epfl.ch). Gene Ontology annotations (UniProt) explicitly associate Rv0311 with the processes of growth (GO:0040007) and pathogenesis (GO:0009405) (orca2.tamu.edu). Experimentally, Rv0311 has been shown to be required for optimal growth under certain conditions: a high-throughput mutagenesis study identified Rv0311 as essential for growth in standard minimal media (orca2.tamu.edu). In particular, a transposon insertion in Rv0311 severely impaired M. tuberculosis growth on laboratory agar (7H10) and in infected mice, suggesting involvement in vital metabolic or replicative processes (orca2.tamu.edu) (mycobrowser.epfl.ch). Conversely, in nutrient-rich media, Rv0311 is non-essential (mutants can grow when many nutrients are supplied) (mycobrowser.epfl.ch), implying its process may be bypassed by environmental supplements. This pattern indicates Rv0311 participates in a biosynthetic or nutrient utilization pathway that is indispensable when the bacterium must synthesize its own building blocks, linking it to general growth and metabolism. Rv0311 is also implicated in biological stress responses and virulence pathways. It is part of the SigH and WhiB5 regulons (see Expression section), which are activated during oxidative stress and dormancy, hinting that Rv0311 is involved in the bacterial stress adaptation process (orca2.tamu.edu). Moreover, because Rv0311 mutants are attenuated in vivo (especially in the central nervous system infection model), the gene likely contributes to the infection process and survival inside the host (mycobrowser.epfl.ch). In summary, while the precise process is undetermined, Rv0311 is functionally tied to essential cellular processes (possibly cofactor biosynthesis or cell-wall assembly) and is required for M. tuberculosis to grow, withstand stress, and cause disease.
Rv0311 has drawn interest due to its connection with M. tuberculosis virulence and fitness in infection models. Although not a “disease gene” in the human sense, Rv0311 significantly affects the pathogenicity of the bacterium that causes tuberculosis. In a landmark transposon mutagenesis screen, Rv0311 was identified as essential for M. tuberculosis survival in mice, meaning bacteria lacking Rv0311 could not establish a normal infection (orca2.tamu.edu) (mycobrowser.epfl.ch). Specifically, Sassetti et al. (2003) found Rv0311 mutants were severely under-represented both in vitro on minimal medium and during mouse infection, classifying it as essential for viability (orca2.tamu.edu). A later study by Be et al. (2008) noted that a transposon insertion in the Rv0311 ortholog of strain CDC1551 led to attenuation in the central nervous system of infected mice (mycobrowser.epfl.ch). This suggests Rv0311 is required for M. tuberculosis to invade or proliferate in brain tissues, highlighting a role in tuberculous meningitis or disseminated TB pathogenesis. Furthermore, Rv0311 has been listed among genetic determinants needed for persistence during infection – mutants show defects in surviving the host environment, indicating a virulence phenotype (mycobrowser.epfl.ch). No direct link to human genetic disease exists (since this is a bacterial gene), but from a pathogen perspective, Rv0311 is a candidate virulence factor. Its deletion or disruption leads to loss of fitness in host infection, making it a potential target for attenuated vaccine strains or drug development. Phenotypically, Rv0311 mutants (when obtainable in rich media) do not show growth defects in nutrient-rich laboratory culture (mycobrowser.epfl.ch), but fail to thrive in nutrient-poor or in vivo conditions, reflecting an in vivo-specific requirement. There are no known polymorphisms of Rv0311 directly associated with clinical drug resistance or strain lineages; however, its strong conservation across virulent M. tuberculosis strains suggests it contributes to the pathogenic versatility of the TB bacillus. In summary, Rv0311 is critical for the bacterium’s disease-causing ability, with mutants showing attenuated virulence and impaired survival in host tissues, thereby associating this gene with tuberculosis pathogenesis.
The Rv0311 protein is 409 amino acids in length and displays several noteworthy structural features despite being of unknown function. Bioinformatic analysis indicates an N-terminal signal peptide (approximately the first ~30–35 residues) rich in hydrophobic amino acids, supporting the notion that the protein is exported from the cytosol (mycobrowser.epfl.ch). Importantly, Rv0311’s sequence contains a conserved protein splicing (intein) signature (PROSITE pattern PS00881) (mycobrowser.epfl.ch). Inteins are self-cleaving peptide elements, and the presence of this motif suggests that Rv0311 either contains an intein-like domain or shares a common ancestry with splicing proteins. The signature includes key residues typically required for protein splicing (for example, a conserved cysteine/serine at the intein N-terminus and a His-Asn at the C-terminus). In Rv0311, a histidine–asparate–cysteine motif is present, and overall the protein’s sequence is reminiscent of homing endonucleases or autoprocessing enzymes, though the full splicing mechanism in Rv0311 has not been demonstrated (mycobrowser.epfl.ch). Aside from the intein-like signature, Rv0311 does not belong to any well-characterized protein family – database searches (Pfam, conserved domain databases) return no definitive domains, classifying it as a novel protein fold. In support of this, Rv0311 has no close structural homologs in the Protein Data Bank (no structures above 35% identity) (orca2.tamu.edu). This prompted the modeling of Rv0311: an AlphaFold 3D structure prediction is available (orca2.tamu.edu), which can provide insights into its fold. The predicted structure (AlphaFold DB entry O07238) suggests Rv0311 is a globular protein with mixed α/β secondary structure, potentially forming a two-domain architecture separated by a cleft (speculative based on typical intein-endonuclease arrangements). Any active-site in the model likely centers around the intein motif region, which could coordinate a metal ion or substrate. Additionally, Rv0311 is fairly alanine/glycine-rich in parts (common in several Mtb cell-envelope proteins), and contains scattered proline-rich stretches that might confer structural rigidity or interaction sites. The protein has no predicted transmembrane helices beyond the signal peptide, aligning with its secreted status (orca2.tamu.edu). Taken together, Rv0311 appears to be a secreted enzyme-like protein with an intein/homologous endonuclease signature, indicating a unique autocatalytic or nucleolytic function might be embedded in its structure. Further structural studies or crystallization would be needed to confirm its folding and to identify any catalytic pocket or ligand-binding sites.
Expression of Rv0311 in M. tuberculosis is regulated in concert with stress and virulence programs. While baseline expression data (e.g. during exponential growth) are not highlighted in literature, several high-throughput studies have shed light on when Rv0311 is up- or down-regulated. Notably, ChIP-Seq analyses have identified transcription factors that bind near the Rv0311 promoter, indicating regulatory inputs. The sigma factor SigH (Rv3223c), an alternate sigma known for controlling oxidative stress responses, binds to the Rv0311 locus (orca2.tamu.edu). Another regulator, WhiB5 (Rv0022c), a redox-sensitive transcription factor, also targets the Rv0311 gene promoter (orca2.tamu.edu). These factors typically activate genes during stress conditions such as redox imbalance and envelope stress, suggesting that Rv0311 expression is induced as part of the bacterial stress response and dormancy survival strategy. Supporting this, a study of regulated overexpression (TFOE) found that overexpressing WhiB5 or SigH leads to upregulation of Rv0311 expression, whereas overexpressing an unidentified regulator Rv0576 caused its repression (orca2.tamu.edu). Collectively, these data indicate Rv0311 is positively regulated by stress-response pathways (SigH and WhiB5 regulons) (orca2.tamu.edu). This upregulation is likely to occur during the transition to stationary phase, during infection of macrophages, or upon encountering oxidative stress, conditions where SigH and WhiB5 are active. In contrast, Rv0311 may be down-regulated during optimal growth or certain other conditions (the factor Rv0576 that downregulates it is uncharacterized, but could be part of a nutrient-rich condition response) (orca2.tamu.edu). Transcriptional profiling experiments also hint at Rv0311’s behavior: for instance, one data compendium (Boshoff et al. 2004) reported Rv0311 transcript induction upon exposure to certain drugs, linking it to drug stress responses (orca2.tamu.edu). No dedicated sigma factor consensus has been published for Rv0311, but the involvement of SigH suggests a promoter recognized under extracytoplasmic function (ECF) sigma conditions. On the protein level, Rv0311 has been detected in bacteria grown in vitro under standard conditions (mycobrowser.epfl.ch), confirming it is expressed during laboratory culture. There is no evidence that Rv0311 is only expressed in vivo; rather, it seems to be expressed broadly but upregulated in hostile environments. Overall, Rv0311’s expression is tightly regulated by stress and virulence signals, consistent with a protein that helps the bacillus survive during the stationary phase, within macrophages, or under immune pressure.
Rv0311 is a member of the core set of conserved proteins in the M. tuberculosis complex and beyond. It is present in multiple mycobacterial species, indicating an evolutionarily preserved function. For example, the ortholog in Mycobacterium bovis (Mb0319) is 100% identical to Rv0311 at the amino acid level, reflecting the clonal conservation within the M. tuberculosis/M. bovis lineage (orca1.tamu.edu). Homologs of Rv0311 can be found in diverse slow-growing and rapid-growing mycobacteria. M. marinum (a fish pathogen related to Mtb) carries a corresponding gene (MMAR_0561) sharing ~84% identity (orca1.tamu.edu), and M. avium (MAV_4850) shares ~79% identity (orca1.tamu.edu). Interestingly, the fast-growing saprophyte Mycobacterium smegmatis also possesses a homolog (MSMEG_5855) with ~72% identity to Rv0311 (orca1.tamu.edu). The presence of Rv0311 in M. smegmatis and environmental mycobacteria suggests the gene serves a fundamental metabolic or structural role not limited to pathogenic species (though it may have been co-opted for virulence in M. tuberculosis). Phylogenetically, Rv0311 appears confined to the mycobacterial genus; orthologs are also noted in M. abscessus (72% identity) and M. ulcerans (83% identity) among others, which span both pathogenic and non-pathogenic mycobacteria (orca1.tamu.edu) (orca1.tamu.edu). This broad conservation underscores that Rv0311’s function is likely important for the biology of Mycobacteriaceae in general. An exception to its presence is seen in Mycobacterium leprae, an obligate parasite with a massively reduced genome – M. leprae appears to lack an Rv0311 ortholog (orca1.tamu.edu). The absence in M. leprae, which cannot grow outside a host and has lost many metabolic genes, supports the idea that Rv0311 is involved in a process dispensable in an extremely host-dependent lifestyle (i.e., M. leprae* might obtain the relevant metabolite from the host or no longer requires it). Outside of mycobacteria, close homologs are not documented, implying Rv0311 is part of the Actinobacterial-specific repertoire. It is considered a Conserved Hypothetical in TB databases (mycobrowser.epfl.ch), meaning it has recognizable counterparts in related genomes but no functional annotation. The strong sequence conservation (often >70% identity across millions of years of mycobacterial evolution) indicates purifying selection, suggesting Rv0311 performs a pivotal role that is maintained in these bacteria. Evolutionarily, therefore, Rv0311 represents a highly conserved, likely essential protein among mycobacteria, with potential as a broad-spectrum target (since inhibitors might affect many mycobacterial species). Its conservation also provides opportunities to use surrogate models (like M. smegmatis) to study its function, since the gene is present and similar in those faster-growing relatives.
A variety of experimental approaches have shed light on Rv0311, even as its exact function remains elusive:
Genome Annotation and Initial Discovery: Rv0311 was first noted in the complete H37Rv genome sequence (Cole et al., 1998) as an open reading frame of unknown function. It has since been consistently annotated as a hypothetical protein in databases like TubercuList (orca2.tamu.edu). The Tuberculosis Community Annotation Project also did not assign a function or name to Rv0311, reflecting the difficulty in characterizing it (orca2.tamu.edu).
Proteomic Identification: Rv0311 protein expression was confirmed by proteomic studies. Målen et al. (2010) extracted M. tuberculosis H37Rv proteins with Triton X-114 detergent and identified Rv0311 among the cell envelope-associated proteins (mycobrowser.epfl.ch). This study highlighted Rv0311 as a novel protein present in the membrane fraction. Similarly, de Souza et al. (2011) performed a comprehensive proteomic profiling of culture filtrate, membrane, and whole-cell lysate proteins; Rv0311 was detected in all three compartments (mycobrowser.epfl.ch). These findings are pivotal, as they validate that Rv0311 is expressed in M. tuberculosis and is exported, supporting hypotheses about its location and possible interaction with the host or cell wall.
Transposon Mutagenesis and Essentiality: A key line of evidence for Rv0311’s importance comes from transposon mutagenesis screens. Sassetti et al. (2003) conducted a saturated transposon library screen in H37Rv and identified Rv0311 as essential for growth in vitro (on minimal medium 7H10 agar) (orca2.tamu.edu). The same study (and a follow-up in 2003 for in vivo) showed that Rv0311 mutants could not be recovered from mouse spleens, implying essentiality in vivo as well (orca2.tamu.edu). These classic TraSH (transposon site hybridization) experiments first pinpointed Rv0311 as a critical gene. In contrast, a more recent deep TnSeq study by DeJesus et al. (2017) with enriched media reported Rv0311 as non-essential under rich laboratory conditions (mycobrowser.epfl.ch). This discrepancy is reconciled by the medium differences: in nutrient-rich broth, auxotrophic defects can be rescued, whereas minimal media demand Rv0311’s function. A study by Minato et al. (2019) also classified Rv0311 as non-essential in a specialized rich medium (MtbYM), consistent with DeJesus’s findings (mycobrowser.epfl.ch). These comparative studies underscore a conditional essentiality: Rv0311 is indispensable for basic biosynthesis and growth in standard or nutrient-poor conditions, but dispensable when supplements bypass its role.
Virulence and Mutant Phenotypes: An important study by Be et al. (2008) used signature-tagged mutagenesis in M. tuberculosis CDC1551 to screen for genes needed in infection. They found an insertion mutant in the Rv0311 ortholog that was significantly attenuated in the brain of mice (a model of TB meningitis) (mycobrowser.epfl.ch). While that mutant might have grown normally in vitro (since CDC1551 can sometimes differ in gene requirements), it failed in the host environment, reinforcing the concept that Rv0311 contributes to in vivo survival and virulence. No obvious clinical phenotype (like drug resistance or patient-derived mutations) has been tied to Rv0311, but these laboratory mutant studies highlight its role in pathogenesis.
Regulatory Studies: Using ChIP-Seq (Minch et al., 2014), Rv0311 was identified as a target of regulatory proteins SigH and WhiB5, linking it to the oxidative stress response (orca2.tamu.edu). Additionally, Rustad et al. (2014) showed changes in Rv0311 expression upon overexpressing certain transcription factors (notably Rv0311 was upregulated by WhiB5 and SigH, and downregulated by another factor) (orca2.tamu.edu). These experiments provide evidence that Rv0311 is embedded in the regulatory networks that tune M. tuberculosis’s response to stress, although direct stimuli for Rv0311 induction (e.g. heat, oxidative stress, nutrient starvation) remain to be fully characterized in expression profiling studies.
Computational and Structural Analyses: Recent efforts to predict functions for hypothetical proteins have included Rv0311. For instance, a 2019 BMC Genomics analysis by Wang et al. attempted structure-based function predictions for many Mtb proteins, and Rv0311 was evaluated, though it remains in the “predicted enzyme” category without a specific assignment (orca2.tamu.edu). In 2021, Modlin et al. in mSystems integrated AlphaFold models and literature curation for many Mtb proteins. While Rv0311 was not explicitly given a new name, the availability of an AlphaFold structure (orca2.tamu.edu) now allows researchers to inspect its predicted active site and fold, generating new hypotheses (for example, it may resemble splicing endonucleases). Thus far, no crystal structure or wet-lab enzymology for Rv0311 has been published, making these computational insights especially valuable for guiding future experiments.
In summary, the body of evidence for Rv0311 – from proteomics confirming its expression and localization, to genetic screens establishing its essentiality and role in virulence, to regulatory and computational analyses suggesting how and when it acts – all converge on the view that Rv0311 is a vital, conserved secreted protein required for M. tuberculosis growth and pathogenesis. This makes Rv0311 a notable target for further study, as understanding its function could reveal a new facet of mycobacterial biology and potentially identify a new target for TB intervention.