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Role of lysine‐195 in the KMSKS sequence of E. coli tryptophanyl‐tRNA synthetase
Author(s) -
Chan Kim W.,
Koeppe Roger E.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00274-d
Subject(s) - aminoacylation , enzyme kinetics , aminoacyl trna synthetase , transfer rna , lysine , pyrophosphate , mutant , biochemistry , alanine , enzyme , chemistry , biology , stereochemistry , amino acid , rna , active site , gene
Lysine 195 in the K 195 MSKS sequence of E. coli tryptophanyl‐tRNA synthetase (TrpRS) was replaced with alanine. The resulting K195A mutant TrpRS had essentially unchanged K m values for ATP and Trp, but a 1500‐fold decreased k cat in a pyrophosphate‐ATP exchange reaction. This large decrease in k cat reduces the rate of aminoacyladenylate formation (step 1) to a rate comparable to the rate of aminoacylation of tRNAT 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.