Role of lysine-195 in the KMSKS sequence of E. coli tryptophanyl-tRNA synthetase

FEBS Lett. 1995 Apr 17;363(1-2):33-6. doi: 10.1016/0014-5793(95)00274-d.

Abstract

Lysine 195 in the K195 MSKS sequence of E. coli tryptophanyl-tRNA synthetase (TrpRS) was replaced with alanine. The resulting K195A mutant TrpRS had essentially unchanged Km values for ATP and Trp, but a 1500-fold decreased kcat in a pyrophosphate-ATP exchange reaction. This large decrease in kcat reduces the rate of aminoacyladenylate formation (step 1) to a rate comparable to the rate of aminoacylation of tRNA(Trp) (step 2) by the K195A mutant enzyme. Both the TIGN and KMSKS sequences are important for step 1 of class I aminoacyl-tRNA synthetase reactions.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Alanine
  • Amino Acid Sequence
  • Base Sequence
  • Escherichia coli / enzymology*
  • Kinetics
  • Lysine / chemistry*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Phosphates / metabolism
  • Tryptophan-tRNA Ligase / chemistry*
  • Tryptophan-tRNA Ligase / genetics
  • Tryptophan-tRNA Ligase / metabolism

Substances

  • Phosphates
  • Adenosine Triphosphate
  • Tryptophan-tRNA Ligase
  • Lysine
  • Alanine