J. Biochem, 1983, Vol. 94, No. 1 79-85
© 1983 Japanese Biochemical Society
research-article |
Studies on the High Molecular Weight Form of Polypeptide Chain Elongation Factor-1 from Pig liver. III. Temperature-Dependent Dissociation into Subunits in the Presence of GTP1
Institute of Medical Science, The University of Tokyo Minato-ku, Tokyo 108
Dissociation of highly purified EF-1
ß
(a high molecular weight form of polypeptide chain elongation factor-1) from pig liver into EF-l and EF-1ß at various temperatures was examined and the following results were obtained. (1) When dissociation of EF-lß was analyzed by gel filtration with Sephacryl S-200, it was found that in the absence of GTP, it did not dissociate at any temperature between 4 and 37°C, whereas in the presence of GTP, it tended to dissociate with elevation of the temperature, and almost complete dissociation was observed at 32°C This indicated that the dissociation constant of EF-1ß into EF-l and EF-1ß in the presence of GTP increased with increase in the temperature, (ii) When gel filtration was performed in the presence of both GTP and [14C]Phe-tRNA, the formation of a ternary complex of EF-l-GTP-[14C]Phe-tRNA from EF-lß was noted, and its amount was found to increase with elevation of the temperature, (iii) The amount of [14C]Phe-tRNA bound to ribosomes dependent on added EF-lß similarly increased with increase in the temperature, as in the case of ternary complex formation, whereas the binding of [14C]Phe-tRNA to ribosomes dependent on free EF-l proceeded fairly well even at 0°C. From these results we concluded that among the reaction steps in the binding of [14C]Phe-tRNA to ribosomes dependent on EF-lß, dissociation of EF-lß to form EF-l-GTP and EF-lß in the presence of GTP is the step which is strongly influenced by temperature.
1 This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.
2 Present address: Cancer Institute, Kami-JJcebukuro, Toshima-ku, Tokyo 170.
3 Present address: Department of Physiological Chemistry, The Tokyo Metropolitan Institute of Medical Science, 3-18 Honkomagome, Bunkyo-ku, Tokyo 113. To whom requests for reprints should be addressed.