The primary structure of elongation factor G from Escherichia coli Amino acid sequence of the region containing the GTP-binding center

Abstract

The protein biosynthesis elongation factor EF-G has an exposed SH-group, the modification of which results in the inhibition of the uncoupled GTPase reaction [ 1,2] . This SH-group seems to be contained in the GTP-binding region of EF-G since it was shown in our laboratory that the region including the exposed SH-group is labelled by the photoactivated GTP analogs with a high specificity [3]. Moreover it is known that guanyl nucleotides protect this group from thiol reagents [4]. EF-G incubation with trypsin results in the formation of several fragments comparatively stable to further trypsin treatment [5]. A detailed study of the fragments formed by limited trypsinolysis of EF-G modified by [ 14C ] labeled ICHzCONHz at the exposed SH-group has shown that this SH-group is located in the N-terminal region of EF-G [6]. In this paper we present the amino acid sequence of the fragment containing the exposed SH-group and apparently participating in the formation of the GTPbinding center. The fragment consists of 69 amino acid residues, the only cysteine residue being in position 5.5.