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Mycobacterium tuberculosis ArfA Rv0899: Difference between revisions

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2. Rapid ammonia secretion to external environment:
2. Rapid ammonia secretion to external environment:
deamidation of the amino acid pair <scene name='61/612805/Asn111_and_gly112/1'> Asn111-Gly112 </scene>, located at the end of α1 and preceding L3, a pH-dependent reaction whereby Asn is converted to Asp and ammonia is released. Asparagine residues preceding glycine, and situated in conformationally flexible regions of proteins, are frequently deamidated, with potentially significant consequences for protein regulation and function <ref>PMID: 20199110</ref>. [[Image:Asparaginase-reaction.jpg|250px]]
deamidation of the amino acid pair <scene name='61/612805/Asn111_and_gly112/1'> Asn111-Gly112 </scene>, located at the end of α1 and preceding L3, a pH-dependent reaction whereby Asn is converted to Asp and ammonia is released. Asparagine residues preceding glycine, and situated in conformationally flexible regions of proteins, are frequently deamidated, with potentially significant consequences for protein regulation and function <ref>PMID: 20199110</ref>. [[Image:Asparaginase-reaction.jpg|250px]]


3. Stabilization of the outer membrane:
3. Stabilization of the outer membrane:
1. pH-dependent conformational dynamics of hydrophobic cluster of L232, F225, L240, A244, V281, L285 <scene name='61/612805/D236_before_mutation/1'>in neutral pH (D236) </scene> that folds to a more ordered structure like a flap at <scene name='61/612805/D236a_after_mut/3'>acidic pH (D236A) </scene>.
1. pH-dependent conformational dynamics of hydrophobic cluster of L232, F225, L240, A244, V281, L285 <scene name='61/612805/D236_before_mutation/1'>in neutral pH (D236) </scene> that folds to a more ordered structure like a flap at <scene name='61/612805/D236a_after_mut/3'>acidic pH (D236A) </scene>.


2. binding to peptidoglycan and phospholipid layer.
a) The B domain has homology with conserved putative <scene name='61/612805/Conserved_g95_and_g164_in_bon/2'>lipid-binding BON</scene> (bacterial OsmY and nodulation) superfamily domains and conserved Gly95 and Gly164 [http://www.ebi.ac.uk/interpro/entry/IPR014004], which putative function is phospolipid binding, nitrogen fixation and / or nitrogen metabolism <ref>PMID: 12878000 </ref>.


b)The C domain has homology to the OmpA-C-like superfamily of periplasmic peptidoglycan-binding sequences, found in several types of bacterial membrane proteins.Contribution for structural strength to the bacterial cell wall under acid or other stress conditionsIts functions by binding to peptidoglycan biosyntheesis intermediate uridine-5-'-diphosphate-MurNAc–L-Ala–D-γ-Glu–m-DAP–D-Ala–D-Ala (UMDP) [http://en.wikipedia.org/wiki/Peptidoglycan] binding site. <scene name='61/612805/Peptidoglycan_binding_site/1'>(R277, R319, T261, D262, N270)</scene>. These residues are strictly conserved in the OmpA -like family The side chain of m-DAP is stabilized by charge-charge interactions between its electronegative carbonyl group with R277 and R319 guanidinium groups and with the N270 carboxamide and between its electropositive amino group with the D262 carboxyl and the T261 hydroxyl. UMDP could interact through contacts of its γ-Glu3 and Ala2 backbone amides with the side-chain hydroxyl of S266, of its MurNAc O3 with the amide proton of E267, and of its MurNAc NH2 with the E267 carboxyl <ref>PMID: 22206986 </ref>.  
2. Binding to peptidoglycan and phospholipid layer.
a) The B domain has homology with conserved putative <scene name='61/612805/Conserved_g95_and_g164_in_bon/2'>lipid-binding BON</scene> (bacterial OsmY and nodulation) superfamily domains and conserved Gly95 and Gly164 [http://www.ebi.ac.uk/interpro/entry/IPR014004], which putative functions are prevention of shrinkage of inner and outer membrane by binding to the phospholipid layer, nitrogen fixation and / or nitrogen metabolism <ref>PMID: 12878000 </ref>.
 
b)The C domain has homology to the OmpA-C-like superfamily of periplasmic peptidoglycan-binding sequences, found in several types of bacterial membrane proteins.Contribution for structural strength to the bacterial cell wall under acid or other stress conditionsIts functions by binding to peptidoglycan biosyntheesis intermediate uridine-5-'-diphosphate-MurNAc–L-Ala–D-γ-Glu–m-DAP–D-Ala–D-Ala (UMDP) [http://en.wikipedia.org/wiki/Peptidoglycan] binding site. <scene name='61/612805/Peptidoglycan_binding_site/1'>(R277, R319, T261, D262, N270)</scene>. These residues are strictly conserved in the OmpA -like family. The side chain of m-DAP is stabilized by charge-charge interactions between its electronegative carbonyl group with R277 and R319 guanidinium groups and with the N270 carboxamide and between its electropositive amino group with the D262 carboxyl and the T261 hydroxyl. UMDP could interact through contacts of its γ-Glu3 and Ala2 backbone amides with the side-chain hydroxyl of S266, of its MurNAc O3 with the amide proton of E267, and of its MurNAc NH2 with the E267 carboxyl <ref>PMID: 22206986 </ref>.  


[[Image:123456.jpg|250px]]                              [[Image:MurNac11.jpg|250px]]
[[Image:123456.jpg|250px]]                              [[Image:MurNac11.jpg|250px]]

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Liliya Karasik, Michal Harel, Jaime Prilusky
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