title: Kinetic studies on the role of elongation factors 1 beta and 1 gamma in protein synthesis.
abstract: An equilibrium isotope exchange technique was used to measure in an Artemia system the catalytic influence of elongation factor (EF) 1 beta gamma on the dissociation of GDP from the complex of elongation factor 1 alpha.[3H] GDP in the presence of an excess of free GDP. The kinetic data demonstrate that, in analogy to procaryotes, dissociation of GDP occurs via the formation of a transient ternary complex of EF-1 alpha.GDP.EF-1 beta gamma. The rate constants for the dissociation of GDP from EF-1 alpha.GDP and from the ternary complex EF-1 alpha.GDP.EF-1 beta gamma were found to be 0.7 x 10(-3) and greater than or equal to 0.7 s-1, respectively. The equilibrium association constants of GDP to EF-1 alpha.EF-1 beta gamma and of EF-1 beta gamma to EF-1 alpha.GDP were found to be 2.3 x 10(5) and 4.2 x 10(5) M-1, respectively. Judged from the known elongation rate in vivo and kinetic constants of nucleotide exchange, it was estimated that the recycling of EF-1 alpha may be a rate-controlling step in eucaryotic translation. As a model for GTP exchange, the formation of the ternary EF-1 alpha.guanylyl (beta gamma-methylene)diphosphonate.EF-1 beta gamma complex was also studied. It was observed that both an increase of the level of aminoacyl-tRNA and of temperature favored the dissociation of this complex, thereby enabling EF-1 beta gamma to recycle as a catalyst. This behavior would explain the frequent occurrence of a heavy form of elongation factor 1 in extracts of the eucaryotic cell.
authors.affiliation: Laboratory for Physiological Chemistry, Sylvius Laboratories, Leiden, The Netherlands.
authors.forename: G M
authors.initials: GM
authors.lastname: Janssen
authors.forename: W
authors.initials: W
authors.lastname: Möller
mesh_terms: D000465:Algorithms; D000818:Animals; D001156:Artemia; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000502:physiology*; D014176:Protein Biosynthesis
chemical_list: D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate