Interaction of Subunits of Polypeptide Chain Elongation Factor 1 from Pig Liver

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Abstract
In the preceding papers, we showed that one of the two complementar factors of polypeptide chain elongation factor 1 (EF-1) from pig liver, EF-1α, functionally corresponds to bacterial EF-Tu (Nagate, S., Iwasaki, K., and kaziro, Y. (1976) Arch. Biochem. Biophys. 172, 168), while the other, EF-1β, corresponds to bacterial EF-Ts (Motoyoshi, K. and Iwasaki, K. (1977) J. Biochem. 82, 703). Therefore, the interaction between EF-1α and EF-1βγ or EF-1β was examined and the following results were obtained. i) EF-1βγ catalytically promoted the exchange of [14C]GDP bound to EF-1α with exogenous [3H]GDP. ii) In the absence of the exogenous guanine nucleotide, EF-1βγ as well as an EF-1α-EF-1βcomplex. iii) The occurrence of EF-1α EF-1βγ and EF-1β complexes was demonstrated by gel filtration on Sephadex G-150. These results stongly indicate that the mechanism of the saction of Ef-1βγ or EF-1β in coverting Ef-1α-GDP into EF-1α-GTP is analogous to bacterial EF-Ts, and the reaction is accomplised by the following reactions;