Crystal structure of a SAM-dependent methyltransferase LepI in complex with its substrate

Experimental Data Snapshot

  • Resolution: 2.24 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.198 
  • R-Value Observed: 0.199 

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Deciphering the regulatory and catalytic mechanisms of an unusual SAM-dependent enzyme.

Sun, Q.Hu, Y.Gu, Y.Huang, J.He, J.Luo, L.Yang, Y.Yin, S.Dou, C.Wang, T.Fu, X.He, L.Qi, S.Zhu, X.Yang, S.Wei, X.Cheng, W.

(2019) Signal Transduct Target Ther 4: 17-17

  • DOI: https://doi.org/10.1038/s41392-019-0052-y
  • Primary Citation of Related Structures:  
    6J1O, 6J24, 6J46

  • PubMed Abstract: 

    S -adenosyl-1-methionine (SAM)-dependent enzymes regulate various disease-related behaviors in all organisms. Recently, the leporin biosynthesis enzyme LepI, a SAM-dependent enzyme, was reported to catalyze pericyclic reactions in leporin biosynthesis; however, the mechanisms underlying LepI activation and catalysis remain unclear. This study aimed to investigate the molecular mechanisms of LepI. Here, we reported crystal structures of LepI bound to SAM/5'-deoxy-5'-(methylthio) adenosine (MTA), S -adenosyl-homocysteine (SAH), and SAM/substrate states. Structural and biochemical analysis revealed that MTA or SAH inhibited the enzyme activities, whereas SAM activated the enzyme. The analysis of the substrate-bound structure of LepI demonstrated that this enzymatic retro-Claisen rearrangement was primarily driven by three critical polar residues His133, Arg197, Arg295 around the active site and assisted by SAM with unclear mechanism. The present studies indicate that the unique mechanisms underlying regulatory and catalysis of the unusual SAM-dependent enzyme LepI, not only strengthening current understanding of the fundamentally biochemical catalysis, but also providing novel insights into the design of SAM-dependent enzyme-specific small molecules.

  • Organizational Affiliation

    3Department of Medicinal Chemistry, Key Laboratory of Drug-Targeting and Drug Delivery System of the Education Ministry, Sichuan Engineering Laboratory for Plant-Sourced Drug and Sichuan Research Center for Drug Precision Industrial Technology, West China School of Pharmacy, Sichuan University, Chengdu, 610041 China.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
O-methyltransferaseA [auth B],
B [auth A]
387Aspergillus flavusMutation(s): 0 
Gene Names: COH21_002903
Find proteins for B8NJH3 (Aspergillus flavus (strain ATCC 200026 / FGSC A1120 / IAM 13836 / NRRL 3357 / JCM 12722 / SRRC 167))
Explore B8NJH3 
Go to UniProtKB:  B8NJH3
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupB8NJH3
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on SAM

Download Ideal Coordinates CCD File 
D [auth B],
F [auth A]
C15 H22 N6 O5 S
Query on BYO

Download Ideal Coordinates CCD File 
C [auth B],
E [auth A]
C22 H25 N O2
Experimental Data & Validation

Experimental Data

  • Resolution: 2.24 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.198 
  • R-Value Observed: 0.199 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 160.445α = 90
b = 62.151β = 112.88
c = 112.296γ = 90
Software Package:
Software NamePurpose
HKL-3000data reduction
HKL-3000data scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
National Natural Science Foundation of ChinaChina21702141

Revision History  (Full details and data files)

  • Version 1.0: 2019-05-01
    Type: Initial release
  • Version 1.1: 2019-11-13
    Changes: Database references
  • Version 1.2: 2023-11-22
    Changes: Data collection, Database references, Refinement description