A structural model for elongation factor 1 (EF-1) and phosphorylation by protein kinase CKII.
EF-1alpha binds aminoacyl-tRNA to the ribosome with the hydrolysis of GTP; the betagammadelta complex facilitates the exchange of GDP for GTP to initiate another round of elongation. To examine the subunit structure of EF-1 and phosphorylation by protein kinase CKII, recombinant beta, gamma, and delta subunits from rabbit were expressed in E. coli and the subunits were reconstituted into partial and complete complexes and analyzed by gel filtration. To determine the availability of the beta and delta subunits for phosphorylation by CKII, the subunits and the reconstituted complexes were examined as substrates for CKII. Formation of the nucleotide exchange complex increased the rate of phosphorylation of the beta subunit and reduced the Km, while addition of alpha to beta or the betagammacomplex inhibited phosphorylation by CKII. However, alpha had little effect on phosphorylation of delta. Thus, the beta and delta subunits in EF-1 were differentially phosphorylated by CKII, in that phosphorylation of beta was altered by association with other subunits, while the site on delta was always available for phosphorylation by CKII. From the availability of the subunits for phosphorylation by CKII and the composition of the reconstituted partial and complete complexes, a model for the subunit structure of EF-1 consisting of(alpha2betagamma2delta)2 is proposed and discussed.
Sheu
G T
GT
Department of Biochemistry and Genetics Graduate Group, University of California, Riverside 92521, USA.
Traugh
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008956:Models, Chemical; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D011994:Recombinant Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases