Effect of Thermus thermophilus elongation factor Ts on the conformation of elongation factor Tu

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Abstract
Affinity labeling in situ of the Thermus thermophilus elongation factor Tu (EF‐Tu) nucleotide binding site was achieved with periodate‐oxidized GDP (GDPoxi) or GTP (GTPoxi) in the absence and presence of elongation factor Ts (EF‐Ts). Lys52 and Lys137, both reacting with GDPoxi and GTPoxi, are located in the nucleotide binding region. In the absence of EF‐Ts Lys137 and to a lesser extent Lys52 were accessible to the reaction with GTPoxi, GDPoxi reacted much more efficiently with Lys52 than with Lys137 under these conditions [Peter, M. E., Wittman‐Liebold, B. & Sprinzl, M. (1988) Biochemistry 27, 9132–9138]. In the presence of EF‐Ts, GDPoxi reacted more efficiently with Lys137 than with Lys52, indicating that the interaction of EF‐Ts with EF‐Tu˙ GDPoxi induces a conformation resembling that of the EF‐Tu˙ GTPoxi complex in the absence of EF‐Ts. Binding of EF‐Ts to EF‐Tu˙ GDP enhances the accessibility of the Arg59‐Gly60 peptide bond of EF‐Tu to trypsin cleavage. Hydrolysis of this peptide bond does not interfere with the ability of EF‐Ts to bind to EF‐Ts. EF‐Ts is protected against trypsin cleavage by interaction with EF‐Tu˙ GDP. High concentrations of EF‐Ts did not interfere significantly with aminoacyl‐tRNA˙ EF–Tu˙ GTP complex formation.

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