Structural and stereochemical analysis of a modular polyketide synthase ketoreductase domain required for the generation of a cis-alkene

Chem Biol. 2013 Jun 20;20(6):772-83. doi: 10.1016/j.chembiol.2013.04.014.

Abstract

The formation of an activated cis-3-cyclohexylpropenoic acid by Plm1, the first extension module of the phoslactomycin polyketide synthase, is proposed to occur through an L-3-hydroxyacyl-intermediate as a result of ketoreduction by an A-type ketoreductase (KR). Here, we demonstrate that the KR domain of Plm1 (PlmKR1) catalyzes the formation of an L-3-hydroxyacyl product. The crystal structure of PlmKR1 revealed a well-ordered active site with a nearby Trp residue characteristic of A-type KRs. Structural comparison of PlmKR1 with B-type KRs that produce D-3-hydroxyacyl intermediates revealed significant differences. The active site of cofactor-bound A-type KRs is in a catalysis-ready state, whereas cofactor-bound B-type KRs are in a precatalytic state. Furthermore, the closed lid loop in substrate-bound A-type KRs restricts active site access from all but one direction, which is proposed to control the stereochemistry of ketoreduction.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alcohol Oxidoreductases / chemistry
  • Alcohol Oxidoreductases / metabolism*
  • Alkenes / chemistry
  • Alkenes / metabolism*
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Biocatalysis
  • Catalytic Domain
  • Crystallography, X-Ray
  • Kinetics
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Stereoisomerism
  • Substrate Specificity

Substances

  • Alkenes
  • Bacterial Proteins
  • Alcohol Oxidoreductases
  • polyketide synthase ketoreductase

Associated data

  • PDB/4HXY