Interaction of the N‐Terminal and C‐Terminal Domains of Elongation Factor G on Formation of Complexes with Guanyl Nucleotides

Publisher Website
Google Scholar
Abstract
Polarized fluorescence studies of interaction between guanyl nucleotides (GTP and GDP) and elongation factor G and its N‐terminal tryptic fragment T*2, carrying a fluorescent group (aminorhodamine B) at the exposed cysteine residue, has shown that binding of nucleotides by an intact EF‐G molecule at neutral pH essentially affects the mobility of the fluorescent group. GTP binding changes its relaxation properties to a greater extent than GDP binding. At the same time it was demonstrated that the spectrum of relaxation times of the fluorescent group practically does not change on binding of nucleotides by the N‐terminal fragment T*2 (in the absence of the C‐terminal uomain) or in the case when the three‐dimensional structure of the intact EF‐G molecule is destabilized (pH 10). Comparison of the relaxation properties of EF‐G and its N‐terminal fragment T*2, carrying a fluorescent group at the exposed cysteine residue, at pH 7.5 and 10, indicates that the C‐terminal domain is involved in the formation of the close environment of the exposed cysteine residue located in the N‐terminal part of EF‐G.A conclusion is drawn on the nucleotide‐induced influence of the C‐terminal domain on a change of the exposed cysteine residue environment on guanyl nucleotide binding with EF‐G at neutral pH and a hypothetical model of the EF‐G molecule is proposed.