Yeast seryl‐tRNA synthetase expressed in Escherichia coli recognizes bacterial serine‐specific tRNAs in vivo

Abstract

The Saccharomyces cerevisiae serS gene which encodes seryl‐tRNA synthetase (SerRS) was expressed in Escherichia coli from the promoter and the ribosome binding sequences contained in its own 5′‐flanking region. The low level of yeast SerRS in the prokaryotic host was sufficient to permit in vivo complementation of two temperature‐sensitive E. coli serS mutants at the nonpermissive temperature. Thus, yeast SerRS can aminoacylate E. coli tRNASer species in vivo. Yeast SerRS, isolated from an overexpressing E. coli strain by a rapid two‐step purification on FPLC, aminoacylated E. coli tRNA with serine much more poorly (relative kcat/Km= 2 × 10−4) than its homologous tRNAs. DL‐Serine hydroxamate, an inhibitor of E. coli SerRS, inhibits yeast SerRS in vivo and in vitro with an inhibition constant (K1) of 2.7 mM, a value 90‐fold higher than that for E. coli SerRS. Copyright © 1993, Wiley Blackwell. All rights reserved