Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Free: 0.276 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.194 

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An interfacial mechanism and a class of inhibitors inferred from two crystal structures of the Mycobacterium tuberculosis 30 kDa major secretory protein (Antigen 85B), a mycolyl transferase.

Anderson, D.H.Harth, G.Horwitz, M.A.Eisenberg, D.

(2001) J Mol Biol 307: 671-681

  • DOI: https://doi.org/10.1006/jmbi.2001.4461
  • Primary Citation of Related Structures:  
    1F0N, 1F0P

  • PubMed Abstract: 

    The Mycobacterium tuberculosis 30 kDa major secretory protein (antigen 85B) is the most abundant protein exported by M. tuberculosis, as well as a potent immunoprotective antigen and a leading drug target. A mycolyl transferase of 285 residues, it is closely related to two other mycolyl transferases, each of molecular mass 32 kDa: antigen 85A and antigen 85C. All three catalyze transfer of the fatty acid mycolate from one trehalose monomycolate to another, resulting in trehalose dimycolate and free trehalose, thus helping to build the bacterial cell wall. We have determined two crystal structures of M. tuberculosis antigen 85B (ag85B), initially by molecular replacement using antigen 85C as a probe. The apo ag85B model is refined against 1.8 A data, to an R-factor of 0.196 (R(free) is 0.276), and includes all residues except the N-terminal Phe. The active site immobilizes a molecule of the cryoprotectant 2-methyl-2,4-pentanediol. Crystal growth with addition of trehalose resulted in a second ag85B crystal structure (1.9 A resolution; R-factor is 0.195; R(free) is 0.285). Trehalose binds in two sites at opposite ends of the active-site cleft. In our proposed mechanism model, the trehalose at the active site Ser126 represents the trehalose liberated by temporary esterification of Ser126, while the other trehalose represents the incoming trehalose monomycolate just prior to swinging over to the first trehalose site to displace the mycolate from its serine ester. Our proposed interfacial mechanism minimizes aqueous exposure of the apolar mycolates. Based on the trehalose-bound structure, we suggest a new class of antituberculous drugs, made by connecting two trehalose molecules by an amphipathic linker.

  • Organizational Affiliation

    UCLA-DOE Laboratory of Structural Biology and Molecular Medicine, University of California, Los Angeles, CA 90095-1570, USA. dha@mbi.ucla.edu

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
ANTIGEN 85B285Mycobacterium tuberculosisMutation(s): 0 
Membrane Entity: Yes 
Find proteins for P9WQP1 (Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv))
Explore P9WQP1 
Go to UniProtKB:  P9WQP1
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP9WQP1
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Free: 0.276 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.194 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 73.21α = 90
b = 73.21β = 90
c = 92.544γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-01-24
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2018-01-31
    Changes: Experimental preparation
  • Version 1.4: 2024-04-03
    Changes: Data collection, Database references, Derived calculations, Refinement description