F-actin bundling activity of Tetrahymena elongation factor 1 alpha is regulated by Ca2+/calmodulin.
Translation elongation factor 1 alpha (EF-1 alpha) catalyzes the GTP-dependent binding of amino-acyl-tRNA to the ribosome. Previously, Tetrahymena 14-nm filament-associated protein was identified as EF-1 alpha [Kurasawa et al. (1992) Exp. Cell Res. 203, 251-258]. This and several other studies suggest that EF-1 alpha functions not only in translation but also in regulation of some part of the cytoskeleton. Tetrahymena EF-1 alpha bound to F-actin and induced bundling of F-actin. We investigated the effects of GTP/GDP and Ca2+/calmodulin on F-actin bundling activity of EF-1alpha. The presence of GTP, GDP, or guanylyl-imidodiphosphate (GMP-PNP) slightly decreased the amount of EF-1 alpha which bound to F-actin, but each had virtually no effect on the F-actin bundling activity. The formation of F-actin bundles by EF-1 alpha was Ca(2+)-insensitive. In the absence of Ca2+, calmodulin did not bind to EF-1 alpha and F-actin. On the other hand, in the presence of Ca2+, calmodulin directly bound to EF-1 alpha but did not have any serious influence on EF-1 alpha/F-actin binding. Under the conditions, electron microscopy demonstrated that Ca2+/calmodulin completely inhibited the F-actin bundling by EF-1 alpha. These results indicate that CA2+/calmodulin regulates the F-actin bundling activity of EF-1 alpha without inhibition of the binding between Ef-1 alpha and F-actin.
Kurasawa
Y
Y
Institute of Biological Sciences, University of Tsukuba, Ibaraki.
Hanyu
K
K
Watanabe
Y
Y
Numata
O
O
D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000378:metabolism / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects*; D004533:Egtazic Acid / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism / Q000494:pharmacology; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000494:pharmacology*; D013769:Tetrahymena pyriformis / Q000378:metabolism / Q000648:ultrastructure*
D000199:Actins; D002147:Calmodulin; D002614:Chelating Agents; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D006153:Guanosine Diphosphate; D006165:Guanylyl Imidodiphosphate; D004533:Egtazic Acid; D006160:Guanosine Triphosphate; D002118:Calcium