Rv0898c (MYCTU) Research Notes

Gene overview

Rv0898c encodes a small (87 aa, 9.9 kDa) conserved hypothetical protein in Mycobacterium tuberculosis H37Rv. It is classified as a "conserved hypothetical protein" by MycoBrowser. The protein contains a single domain of unknown function, DUF2630 (Pfam PF10944), corresponding to InterPro family IPR020311. The InterPro entry states: "This entry contains proteins with no known function" and has no GO term mappings (interpro2go is empty for IPR020311). There are ZERO curated GO annotations in GOA for this protein.

Protein characteristics

• 87 amino acids, single DUF2630 domain spanning nearly the entire protein (residues 8-86)
• C-terminal disordered region (residues 67-87)
• No predicted transmembrane domains
• No predicted signal peptide
• No recognizable enzymatic domains
• Detected at the protein level by mass spectrometry PMID:21969609

Genomic context

Rv0898c is located at position 1002441 bp on the minus strand. Its immediate downstream neighbor on the chromosome is Rv0899 (ompA/arfA), which is on the plus strand starting at 1002812 bp. Rv0899 encodes a membrane protein that is part of the arf (ammonia release facilitator) operon (Rv0899-Rv0900-Rv0901). Importantly, Rv0898c is transcribed in the OPPOSITE direction from Rv0899 and is NOT part of this operon.

The Rv0899 operon is well characterized: "the rv0899 gene is part of an operon (rv0899-rv0901) that is required for fast ammonia secretion, pH neutralization and growth of M. tuberculosis in acidic environments" [PMID:21905117, DOI:10.1002/prot.23151]. However, Rv0898c, being on the complementary strand, is not part of this operon and its proximity to Rv0899 does not imply functional linkage.

Sequence homologs

MycoBrowser notes that Rv0898c is "highly similar to CAC01589.1|AL391041 hypothetical protein from Streptomyces coelicolor" and shows some homology to Rv0709, another M. tuberculosis protein. The DUF2630 family (IPR020311) contains 1,938 proteins across 2,221 taxa, all of unknown function. No member of this family has been functionally characterized.

Essentiality and expression

• Non-essential for in vitro growth per transposon mutagenesis studies (MycoBrowser annotation)
• Detected by mass spectrometry in whole cell lysates but NOT in culture filtrate or membrane fractions (MycoBrowser)
• mRNA "up-regulated after 96h of starvation" (MycoBrowser annotation, based on transcriptomics). This is consistent with a role in nutrient stress adaptation, which is a common theme in M. tuberculosis persistence biology PMID:11929527

What is NOT known

• No molecular function has been established experimentally
• No interaction partners have been identified
• No structural data available (though AlphaFold model exists)
• No knockout phenotype beyond non-essentiality in vitro
• The function of the DUF2630 domain family remains entirely uncharacterized across all organisms
• There are no publications in PubMed specifically about Rv0898c (PubMed search for "Rv0898c" in title/abstract returns zero results)

Key references

1. PMID:9634230 - Cole et al. 1998. "Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence." Nature 393:537-544. Original genome sequence.
2. PMID:21969609 - Kelkar et al. 2011. "Proteogenomic analysis of Mycobacterium tuberculosis by high resolution mass spectrometry." Mol Cell Proteomics. Protein detection by MS.
3. PMID:28096490 - DeJesus et al. 2017. "Comprehensive Essentiality Analysis of the Mycobacterium tuberculosis Genome via Saturating Transposon Mutagenesis." mBio. Essentiality analysis.
4. PMID:21905117 - Marassi 2011. "Mycobacterium tuberculosis Rv0899 defines a family of membrane proteins widespread in nitrogen-fixing bacteria." Proteins. Describes the Rv0899 operon context.
5. PMID:11929527 - Betts et al. 2002. "Evaluation of a nutrient starvation model of Mycobacterium tuberculosis persistence by gene and protein expression profiling." Mol Microbiol. Starvation response transcriptomics.