Open AccessStructural Fluctuation of the Polypeptide‐Chain Elongation Factor Tu
Author(s) -
OHTA Shigeo,
NAKANISHI Mamoru,
TSUBOI Masamichi,
ARAI Kenichi,
KAZIRO Yoshito
Publication year - 1977
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1977.tb11773.x
Subject(s) - thermus thermophilus , ef tu , escherichia coli , elongation , polypeptide chain , elongation factor , thermus , chain (unit) , chemistry , microbiology and biotechnology , biology , biochemistry , physics , enzyme , materials science , transfer rna , gene , ribosome , rna , thermophile , ultimate tensile strength , metallurgy , astronomy
The kinetics of hydrogen‐deuterium exchange in the polypeptide chain elongation factor Tu (EF‐Tu) from Escherichia coli and that from Thermus thermophilus HB8 has been examined in aqueous solutions at various pH and temperatures by means of infrared absorption measurements. The free EF‐Tu from E. coli has a greater reaction rate at all pH values and at every temperature than that of the GTP‐bound or GDP‐bound EF‐Tu. The free EF‐Tu from T. thermophilus , on the other hand, has an almost equal reaction rate to that of EF‐Tu · GDP in the temperature range 38–55 °C. For the peptide NH groups belonging to a medium‐labile kinetic class, a small but definite difference in the rate of exchange reaction was observed between EF‐Tu · GDP and EF‐Tu · GTP for both E. coli and T. thermophilus. For less labile peptide NH groups, on the other hand, the rate of the exchange reaction with EF‐Tu · GDP from T. thermophilus is only slightly affected by the pH of the solution at 38°C and 45°C, while the rate constant ( k ) with E. coli EF‐Tu · GDP is pH‐dependent (log k · pH). For T. thermophilus EF‐Tu, heat stability measurements, kinetics of the rates of GDP and GTP dissociation, and circular dichroic measurements have also been made. The molecular basis for the thermostability of T. thermophilus EF‐Tu is discussed.