Elongation Factor T from Bacillus stearothermophilus and Escherichia coli

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Abstract
Homogeneous preparations of elongation factors EF-Tu and EF-Ts from B. stearothermophilus were obtained with specific activities of 20,000 .+-. 2000 and 500,000 .+-. 50,000 units/mg, respectively. By dodecylsulfate-polyacrylamide gel electrophoresis the molecular weight of EF-Tu was found to be 49,000 .+-. 2000 and of EF-Ts 35,500 .+-. 1000. Nucleotide-free EF-Tu was prepared by using ITP as a GDP-binding-site-directed analogue. EF-Tu contained 2 sulfydryl groups, 1 reacting fast and 1 slowly with N-ethylmaleimide and 5,5''-dithio-bis(2-nitrobenzoic acid) under non-denaturing conditions. The same reagents reacted with the 3 sulfhydryl groups of EF-Ts in the native state. The heat stabilities of EF-Tu and EF-Ts are reversed with respect to the Escherichia coli factors, EF-Tu being the more stable protein; even nucleotide-free EF-Tu is relatively stable with a half-life at room temperature of about 35 h.