Function
Protein Rv0899 from Mycobacterium tuberculosis [1] belongs to the OmpA (outer membrane protein A) family of outer membrane proteins.The deletion of this gene impairs the uptake of some water-soluble substances, such as serine, glucose, and glycerol.Using NMR chemical shift perturbation and isothermal calorimetric titration assays, Rv0899 was able to interact with Zn(2+) ions, which may indicate a role for Rv0899 in the process of Zn(2+) acquisition.
[1]
Mycobacterium tuberculosis ArfA (Rv0899) is a membrane protein encoded by an ammonia release facilator operon that is necessary for rapid ammonia secretion, pH neutralization and adaptation to acidic environments in vitro. Its C-terminal domain (C domain) shares significant sequence homology with the OmpA-like family of peptidoglycan-binding domains, suggesting that its physiological function in acid stress protection may be related to its interaction with the mycobacterial cell wall. It exhibits pH-dependent conformational dynamics (with significant heterogeneity at neutral pH and a more ordered structure at acidic pH), which could be related to its acid stress response. The C domain associates tightly with polymeric peptidoglycan isolated from M. tuberculosis. Its functions in acid stress protection and peptidoglycan binding suggest a link between the acid stress response and the physicochemical properties of the mycobacterial cell wall.[2].
Disease
Rv0899 has been proposed to act as an outer membrane porin and to contribute to the bacterium's adaptation to the acidic environment of the phagosome[2] during infection. The gene is restricted to pathogenic mycobacteria and, thus, is an attractive candidate for the development of anti-tuberculosis chemotherapy. [3]
Probably plays a role in ammonia secretion that neutralizes the medium at pH 5.5,and preceded exponential growth of M. tuberculosis, although it does not play a direct role in ammonia transport.[ARFA_MYCTU]. The ompATb operon is necessary for rapid ammonia secretion and adaptation of M. tuberculosis to acidic environments in vitro but not in mice.
[4]
Relevance
Structural highlights
Structure Section
The 326-residue protein contains three domains: an N-terminal domain (residues 1-72) that includes a sequence of 20 hydrophobic amino acids required for membrane translocation, a central B domain (residues 73-200) with homology to the conserved putative lipid-binding BON (bacterial OsmY and nodulation) superfamily[3] , and a C domain (residues 201-326) with homology to the OmpA-C-like superfamily of periplasmic peptidoglycan-binding sequences, found in several types of bacterial membrane proteins. Residues 73-326 form a mixed alpha/beta-globular structure, encompassing two independently folded modules corresponding to the B and C domains connected by a flexible linker. The B domain folds with three parallel/antiparallel alpha-helices packed against six parallel/antiparallel beta-strands that form a flat beta-sheet. The core is hydrophobic, while the exterior is polar and predominantly acidic.[5]
References
- ↑ Li J, Shi C, Gao Y, Wu K, Shi P, Lai C, Chen L, Wu F, Tian C. Structural Studies of Mycobacterium tuberculosis Rv0899 Reveal a Monomeric Membrane-Anchoring Protein with Two Separate Domains. J Mol Biol. 2011 Nov 15. PMID:22108166 doi:10.1016/j.jmb.2011.11.016
- ↑ Yao Y, Barghava N, Kim J, Niederweis M, Marassi FM. Molecular Structure and Peptidoglycan Recognition of Mycobacterium tuberculosis ArfA (Rv0899). J Mol Biol. 2012 Feb 17;416(2):208-20. Epub 2011 Dec 21. PMID:22206986 doi:10.1016/j.jmb.2011.12.030
- ↑ Teriete P, Yao Y, Kolodzik A, Yu J, Song H, Niederweis M, Marassi FM. Mycobacterium tuberculosis Rv0899 Adopts a Mixed alpha/beta-Structure and Does Not Form a Transmembrane beta-Barrel. Biochemistry. 2010 Mar 10. PMID:20199110 doi:10.1021/bi100158s
- ↑ Song H, Huff J, Janik K, Walter K, Keller C, Ehlers S, Bossmann SH, Niederweis M. Expression of the ompATb operon accelerates ammonia secretion and adaptation of Mycobacterium tuberculosis to acidic environments. Mol Microbiol. 2011 May;80(4):900-18. doi: 10.1111/j.1365-2958.2011.07619.x. Epub, 2011 Mar 16. PMID:21410778 doi:http://dx.doi.org/10.1111/j.1365-2958.2011.07619.x
- ↑ Teriete P, Yao Y, Kolodzik A, Yu J, Song H, Niederweis M, Marassi FM. Mycobacterium tuberculosis Rv0899 Adopts a Mixed alpha/beta-Structure and Does Not Form a Transmembrane beta-Barrel. Biochemistry. 2010 Mar 10. PMID:20199110 doi:10.1021/bi100158s
