1q74
From Proteopedia
The Crystal Structure of 1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside Deacetylase (MshB)
Structural highlights
Function[MSHB_MYCTO] Catalyzes the deacetylation of 1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside (GlcNAc-Ins) in the mycothiol (MSH) biosynthesis pathway. Shows some amidase activity toward S-conjugates of mycothiol (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMycothiol (1-D-myo-inosityl 2-(N-acetyl-L-cysteinyl)amido-2-deoxy-alpha-D-glucopyranoside, MSH or AcCys-GlcN-inositol (Ins)) is the major reducing agent in actinomycetes, including Mycobacterium tuberculosis. The biosynthesis of MSH involves a deacetylase that removes the acetyl group from the precursor GlcNAc-Ins to yield GlcN-Ins. The deacetylase (MshB) corresponds to Rv1170 of M. tuberculosis with a molecular mass of 33,400 Da. MshB is a Zn2+ metalloprotein, and the deacetylase activity is completely dependent on the presence of a divalent metal cation. We have determined the x-ray crystallographic structure of MshB, which reveals a protein that folds in a manner resembling lactate dehydrogenase in the N-terminal domain and a C-terminal domain consisting of two beta-sheets and two alpha-helices. The zinc binding site is in the N-terminal domain occupying a position equivalent to that of the NAD+ co-factor of lactate dehydrogenase. The Zn2+ is 5 coordinate with 3 residues from MshB (His-13, Asp-16, His-147) and two water molecules. One water would be displaced upon binding of substrate (GlcNAc-Ins); the other is proposed as the nucleophilic water assisted by the general base carboxylate of Asp-15. In addition to the Zn2+ providing electrophilic assistance in the hydrolysis, His-144 imidazole could form a hydrogen bond to the oxyanion of the tetrahedral intermediate. The extensive sequence identity of MshB, the deacetylase, with mycothiol S-conjugate amidase, an amide hydrolase that mediates detoxification of mycothiol S-conjugate xenobiotics, has allowed us to construct a faithful model of the catalytic domain of mycothiol S-conjugate amidase based on the structure of MshB. The crystal structure of 1-D-myo-inosityl 2-acetamido-2-deoxy-alpha-D-glucopyranoside deacetylase (MshB) from Mycobacterium tuberculosis reveals a zinc hydrolase with a lactate dehydrogenase fold.,Maynes JT, Garen C, Cherney MM, Newton G, Arad D, Av-Gay Y, Fahey RC, James MN J Biol Chem. 2003 Nov 21;278(47):47166-70. Epub 2003 Sep 4. PMID:12958317[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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