Role of Lysine-195 in the Kmsks Sequence of Escherichia-Coli Tryptophanyl-Transfer-Rna Synthetase

by Chan, Kim Wan; Koeppe II, R. Erdman

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 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.

Journal
FEBS Letters
Volume
363
Issue
1-2
Year
1995
Start Page
33
ISBN/ISSN
1873-3468; 0014-5793
DOI
10.1016/0014-5793(95)00274-D