Modification of amino groups in EF-Tu . GTP and the ternary complex EF-Tu . GTP . valyl-tRNAVal

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Abstract
In an attempt to describe the binding region of EF-Tu.cntdot.GTP for aminoacyl-tRNA, the .epsilon.-amino groups of the lysine residues of the protein molecule in the GTP and ternary complexes were modified with ethyl acetimidate. Using [14C]ethyl acetimidate, tryptic digestion, fractionation of peptides by high-performance liquid chromatography and amino acid analysis, all reactive lysine residues could be unambiguously identified; 19 of the 23 lysine residues of EF-Tu were labeled under conditions for ternary complex stability. Of these only 8 showed differences in reactivity between free and complexed EF-Tu.cntdot.GTP. In the ternary complex lysine residues 208 and 390 showed an increase in reactivity (60 and 30%, respectively) and residues 2, 4, 237, 248, 263 and 282 showed a decrease in reactivity (between 85 and 37%) compared to the values observed with EF-Tu.cntdot.GTP. The greatest changes in reactivity were observed for lysine residues 2, 4 and 263. These data can be combined with the available structural information to identify possible areas of contact between the protein and nucleic acid moieties in the ternary complex. [Escherichia coli was used.].