4EWL

Crystal Structure of MshB with glycerol and Acetate bound in the active site

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.189 
  • R-Value Observed: 0.191 

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This is version 1.1 of the entry. See complete history. 


Literature

A new crystal form of MshB from Mycobacterium tuberculosis with glycerol and acetate in the active site suggests the catalytic mechanism.

Broadley, S.G., Gumbart, J.C., Weber, B.W., Marakalala, M.J., Steenkamp, D.J., Sewell, B.T.

(2012) Acta Crystallogr D Biol Crystallogr 68: 1450-1459

  • DOI: 10.1107/S090744491203449X
  • Primary Citation of Related Structures:  
    4EWL

  • PubMed Abstract: 

    • MshB, a zinc-based deacetylase, catalyses a step in the mycothiol biosynthetic pathway that involves the deacetylation of 1-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-D-myo-inositol (GlcNAc-Ins), via cleavage of an amide bond, to 1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-D-myo-inositol (GlcN-Ins) and acetate ...

    MshB, a zinc-based deacetylase, catalyses a step in the mycothiol biosynthetic pathway that involves the deacetylation of 1-O-(2-acetamido-2-deoxy-α-D-glucopyranosyl)-D-myo-inositol (GlcNAc-Ins), via cleavage of an amide bond, to 1-O-(2-amino-2-deoxy-α-D-glucopyranosyl)-D-myo-inositol (GlcN-Ins) and acetate. In this study, MshB was expressed, purified and crystallized. A new crystal form was encountered in 0.1 M sodium acetate, 0.2 M ammonium sulfate, 25% PEG 4000 pH 4.6. The crystals diffracted to 1.95 Å resolution and the resulting electron-density map revealed glycerol and the reaction product, acetate, in the active site. These ligands enabled the natural substrate GlcNAc-Ins to be modelled in the active site with some certainty. One acetate O atom is hydrogen bonded to Tyr142 and is located 2.5 Å from the catalytic zinc. The other acetate O atom is located 2.7 Å from a carboxylate O atom of Asp15. This configuration strongly suggests that Asp15 acts both as a general base catalyst in the nucleophilic attack of water on the amide carbonyl C atom and in its protonated form acts as a general acid to protonate the amide N atom. The configuration of Tyr142 differs from that observed previously in crystal structures of MshB (PDB entries 1q74 and 1q7t) and its location provides direct structural support for recently published biochemical and mutational studies suggesting that this residue is involved in a conformational change on substrate binding and contributes to the oxyanion hole that stabilizes the tetrahedral intermediate.

    Organizational Affiliation: 

    Department of Molecular and Cell Biology, University of Cape Town, University Avenue, Rondebosch, Western Cape 7700, South Africa.



Macromolecules
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(by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
1D-myo-inositol 2-acetamido-2-deoxy-alpha-D-glucopyranoside deacetylase A, B299Mycobacterium tuberculosisMutation(s): 0 
Gene Names: mshB, MT1207, Rv1170
EC: 3.5.1.103
Find proteins for P9WJN3 (Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv))
Explore P9WJN3 
Go to UniProtKB:  P9WJN3
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.189 
  • R-Value Observed: 0.191 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 147.379α = 90
b = 71.903β = 128.29
c = 97.681γ = 90
Software Package:
Software NamePurpose
XSCALEdata scaling
PHENIXrefinement
PDB_EXTRACTdata extraction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-09-26
    Type: Initial release
  • Version 1.1: 2012-11-21
    Changes: Database references