Crystal structure of mutant form Cys115His of Citrobacter freundii methionine γ-lyase complexed with l-norleucine

Biochim Biophys Acta Proteins Proteom. 2017 Sep;1865(9):1123-1128. doi: 10.1016/j.bbapap.2017.06.001. Epub 2017 Jun 6.

Abstract

The mutant form of Citrobacter freundii methionine γ-lyase with the replacement of active site Cys115 for His has been found to be inactive in the γ-elimination reaction of methionine while fully active in the γ-elimination reaction of O-acetyl-l-homoserine and in the β-elimination reaction of S-alk(en)yl-substituted cysteines. In this work, the crystal structure of the mutant enzyme complexed with competitive inhibitor, l-norleucine was determined at 1.45Å resolution. At the enzyme active site the inhibitor proved to be bound both noncovalently and covalently, which corresponds to the two intermediates of the γ- and β-elimination reactions, Michaelis complex and the external aldimine. Analysis of the structure allowed us to suggest the possible reason for the inability of the mutant enzyme to catalyze the physiological reaction.

Keywords: C115H mutant form; Pyridoxal 5′-phosphate-dependent methionine γ-lyase; Three-dimensional structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Carbon-Sulfur Lyases / antagonists & inhibitors
  • Carbon-Sulfur Lyases / chemistry*
  • Carbon-Sulfur Lyases / metabolism
  • Catalytic Domain
  • Citrobacter freundii / enzymology*
  • Citrobacter freundii / genetics
  • Crystallography, X-Ray
  • Models, Molecular
  • Mutation, Missense*
  • Norleucine / metabolism*
  • Point Mutation*
  • Protein Binding
  • Protein Conformation

Substances

  • Bacterial Proteins
  • Norleucine
  • Carbon-Sulfur Lyases
  • L-methionine gamma-lyase