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 GTP.
Dissociation of highly purified EF-1 alpha beta gamma (a high molecular weight form of polypeptide chain elongation factor-1) from pig liver into EF-1 alpha and EF-1 beta gamma at various temperatures was examined and the following results were obtained. (i) When dissociation of EF-1 alpha beta gamma 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 degrees C, whereas in the presence of GTP, it tended to dissociate with elevation of the temperature, and almost complete dissociation was observed at 32 degrees C. This indicated that the dissociation constant of EF-1 alpha beta gamma into EF-1 alpha and EF-1 beta gamma 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-1 alpha . GTP . [14C]Phe-tRNA from EF-1 alpha beta gamma 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-1 alpha beta gamma 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-1 alpha proceeded fairly well even at 0 degrees C. From these results we concluded that among the reaction steps in the binding of [14C]Phe-tRNA to ribosomes dependent on EF-1 alpha beta gamma, dissociation of EF-1 alpha beta gamma to form EF-1 alpha . GTP and EF-1 beta gamma in the presence of GTP is the step which is strongly influenced by temperature.
D000818:Animals; D002850:Chromatography, Gel; D006160:Guanosine Triphosphate; D066298:In Vitro Techniques; D008099:Liver / Q000032:analysis*; D008970:Molecular Weight; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000032:analysis*; D012270:Ribosomes / Q000032:analysis; D013552:Swine; D013696:Temperature
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D006160:Guanosine Triphosphate