Mycobacterium tuberculosis ArfA Rv0899: Difference between revisions
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' size='350' frame='true' align='right' caption='NMR structure of uncharacterized protein Rv0899 (PDB code [[2l26]])' scene='Insert optional scene name here' /> | ' size='350' frame='true' align='right' caption='NMR structure of uncharacterized protein Rv0899 (PDB code [[2l26]])' scene='Insert optional scene name here' /> | ||
== Function == | == Function == | ||
The membrane protein Rv0899 (OmpATb) from Mycobacterium tuberculosis, 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 during infection. The gene is restricted to pathogenic mycobacteria and, thus, is an attractive candidate for the development of anti-tuberculosis chemotherapy. 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, 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, including in the C-terminus of the Escherichia coli outer membrane protein OmpA | The membrane protein Rv0899 (OmpATb) from Mycobacterium tuberculosis, 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]] during infection. The gene is restricted to pathogenic [[mycobacteria]] and, thus, is an attractive candidate for the development of anti-tuberculosis chemotherapy. 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, 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, including in the C-terminus of the Escherichia coli outer membrane protein OmpA. Rv0899 does not form a transmembrane beta-barrel. 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.<ref>PMID: 20199110</ref> | ||
Rv0899 from Mycobacterium tuberculosis belongs to the OmpA (outer membrane protein A) family of outer membrane proteins. | Rv0899 from Mycobacterium tuberculosis 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. It was proposed that Rv0899 forms an [[oligomeric]] channel to carry out such functions.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. | ||
<ref>PMID: 22108166 </ref> | <ref>PMID: 22108166 </ref> | ||
Mycobacterium tuberculosis ArfA (Rv0899) is a membrane protein encoded by an operon that is required for supporting bacterial growth in acidic environments. 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. | Mycobacterium tuberculosis ArfA (Rv0899) is a membrane protein encoded by an operon that is required for supporting bacterial growth in acidic environments. 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. ArfA is identified as a peptidoglycan-binding protein. The C domain of ArfA adopts the characteristic fold of the OmpA-like family. 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 and also associates with a soluble peptide intermediate of peptidoglycan biosynthesis. This enabled us to characterize the peptidoglycan binding site where five highly conserved ArfA residues, including two key arginines, establish the specificity for diaminopimelate- but not Lys-type peptidoglycan. ArfA is the first peptidoglycan-binding protein to be identified in 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.<ref>PMID: 22206986 </ref> | ||
Homeostasis of intracellular pH is a trait critical for survival of Mycobacterium tuberculosis in macrophages. However, mechanisms by which M. tuberculosis adapts to acidic environments are poorly understood | Homeostasis of intracellular pH is a trait critical for survival of Mycobacterium tuberculosis in macrophages. However, mechanisms by which M. tuberculosis adapts to acidic environments are poorly understood. OmpATb is not a general porin. Chemical analysis of low-pH culture filtrates showed that the proteins encoded by the ompATb operon are involved in generating a rapid ammonia burst, which neutralized medium pH and preceded exponential growth of M. tuberculosis. Addition of ammonia accelerated growth of the ompATb operon mutant demonstrating that ammonia secretion is indeed a mechanism by which M. tuberculosis neutralizes acidic environments. Infection experiments revealed that the ompATb operon was not required for full virulence in mice suggesting that M. tuberculosis has multiple mechanisms of resisting phagosomal acidification. The ompATb operon is necessary for rapid ammonia secretion and adaptation of M. tuberculosis to acidic environments in vitro but not in mice. | ||
<ref>PMID: 21410778 </ref> | <ref>PMID: 21410778 </ref> | ||
Revision as of 16:18, 22 December 2014
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FunctionFunction
The membrane protein Rv0899 (OmpATb) from Mycobacterium tuberculosis, 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 during infection. The gene is restricted to pathogenic mycobacteria and, thus, is an attractive candidate for the development of anti-tuberculosis chemotherapy. 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, 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, including in the C-terminus of the Escherichia coli outer membrane protein OmpA. Rv0899 does not form a transmembrane beta-barrel. 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.[1] Rv0899 from Mycobacterium tuberculosis 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. It was proposed that Rv0899 forms an oligomeric channel to carry out such functions.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. [2] Mycobacterium tuberculosis ArfA (Rv0899) is a membrane protein encoded by an operon that is required for supporting bacterial growth in acidic environments. 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. ArfA is identified as a peptidoglycan-binding protein. The C domain of ArfA adopts the characteristic fold of the OmpA-like family. 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 and also associates with a soluble peptide intermediate of peptidoglycan biosynthesis. This enabled us to characterize the peptidoglycan binding site where five highly conserved ArfA residues, including two key arginines, establish the specificity for diaminopimelate- but not Lys-type peptidoglycan. ArfA is the first peptidoglycan-binding protein to be identified in 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.[3] Homeostasis of intracellular pH is a trait critical for survival of Mycobacterium tuberculosis in macrophages. However, mechanisms by which M. tuberculosis adapts to acidic environments are poorly understood. OmpATb is not a general porin. Chemical analysis of low-pH culture filtrates showed that the proteins encoded by the ompATb operon are involved in generating a rapid ammonia burst, which neutralized medium pH and preceded exponential growth of M. tuberculosis. Addition of ammonia accelerated growth of the ompATb operon mutant demonstrating that ammonia secretion is indeed a mechanism by which M. tuberculosis neutralizes acidic environments. Infection experiments revealed that the ompATb operon was not required for full virulence in mice suggesting that M. tuberculosis has multiple mechanisms of resisting phagosomal acidification. The ompATb operon is necessary for rapid ammonia secretion and adaptation of M. tuberculosis to acidic environments in vitro but not in mice. [4]
DiseaseDisease
RelevanceRelevance
Structural highlightsStructural highlights
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ReferencesReferences
- ↑ 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
- ↑ 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
- ↑ 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