F-actin sequesters elongation factor 1alpha from interaction with aminoacyl-tRNA in a pH-dependent reaction.
The machinery of eukaryotic protein synthesis is found in association with the actin cytoskeleton. A major component of this translational apparatus, which is involved in the shuttling of aa-tRNA, is the actin-binding protein elongation factor 1alpha (EF-1alpha). To investigate the consequences for translation of the interaction of EF-1alpha with F-actin, we have studied the effect of F-actin on the ability of EF-1alpha to bind to aa-tRNA. We demonstrate that binding of EF-1alpha:GTP to aa-tRNA is not pH sensitive with a constant binding affinity of approximately 0.2 microM over the physiological range of pH. However, the sharp pH dependence of binding of EF-1alpha to F-actin is sufficient to shift the binding of EF-1alpha from F-actin to aa-tRNA as pH increases. The ability of EF-1alpha to bind either F-actin or aa-tRNA in competition binding experiments is also consistent with the observation that EF-1alpha's binding to F-actin and aa-tRNA is mutually exclusive. Two pH-sensitive actin-binding sequences in EF-1alpha are identified and are predicted to overlap with the aa-tRNA-binding sites. Our results suggest that pH-regulated recruitment and release of EF-1alpha from actin filaments in vivo will supply a high local concentration of EF-1alpha to facilitate polypeptide elongation by the F-actin-associated translational apparatus.
Liu
G
G
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Tang
J
J
Edmonds
B T
BT
Murray
J
J
Levin
S
S
Condeelis
J
J
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D003599:Cytoskeleton / Q000737:chemistry / Q000502:physiology; D004023:Dictyostelium / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D014176:Protein Biosynthesis / Q000502:physiology; D011487:Protein Conformation; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000199:Actins; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D012346:RNA, Transfer, Amino Acyl; D011993:Recombinant Fusion Proteins; D006160:Guanosine Triphosphate