Crystal structure of MtmC in complex with SAH

Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.205 

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This is version 1.4 of the entry. See complete history


Structural Insight into MtmC, a Bifunctional Ketoreductase-Methyltransferase Involved in the Assembly of the Mithramycin Trisaccharide Chain.

Chen, J.M.Hou, C.Wang, G.Tsodikov, O.V.Rohr, J.

(2015) Biochemistry 54: 2481-2489

  • DOI: https://doi.org/10.1021/bi501462g
  • Primary Citation of Related Structures:  
    4RV9, 4RVD, 4RVF, 4RVG, 4RVH

  • PubMed Abstract: 

    More and more post-PKS tailoring enzymes are recognized as being multifunctional and codependent on other tailoring enzymes. One of the recently discovered intriguing examples is MtmC, a bifunctional TDP-4-keto-d-olivose ketoreductase-methyltransferase, which-in codependence with glycosyltransferase MtmGIV-is a key contributor to the biosynthesis of the critical trisaccharide chain of the antitumor antibiotic mithramycin (MTM), produced by Streptomyces argillaceus. We report crystal structures of three binary complexes of MtmC with its methylation cosubstrate SAM, its coproduct SAH, and a nucleotide TDP as well as crystal structures of two ternary complexes, MtmC-SAH-TDP-4-keto-d-olivose and MtmC-SAM-TDP, in the range of 2.2-2.7 Å resolution. The structures reveal general and sugar-specific recognition and catalytic structural features of MtmC. Depending on the catalytic function that is conducted by MtmC, it must bind either NADPH or SAM in the same cofactor binding pocket. A tyrosine residue (Tyr79) appears as a lid covering the sugar moiety of the substrate during the methyl transfer reaction. This residue swings out of the active site by ~180° in the absence of the substrate. This unique conformational change likely serves to release the methylated product and, possibly, to open the active site for binding the bulkier cosubstrate NADPH prior to the reduction reaction.

  • Organizational Affiliation

    Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, Kentucky 40536-0596, United States.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
D-mycarose 3-C-methyltransferase426Streptomyces argillaceusMutation(s): 0 
Gene Names: mtmC
Find proteins for Q194Q4 (Streptomyces argillaceus)
Explore Q194Q4 
Go to UniProtKB:  Q194Q4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ194Q4
Sequence Annotations
  • Reference Sequence
Small Molecules
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.241 
  • R-Value Work: 0.203 
  • R-Value Observed: 0.205 
  • Space Group: I 41 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 134.245α = 90
b = 134.245β = 90
c = 130.01γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-02-04
    Type: Initial release
  • Version 1.1: 2015-03-18
    Changes: Database references
  • Version 1.2: 2015-05-13
    Changes: Database references
  • Version 1.3: 2023-09-20
    Changes: Data collection, Database references, Derived calculations, Refinement description
  • Version 1.4: 2023-12-06
    Changes: Data collection