Interaction of elongation factor 1α from Zea mays (ZmEF-1α) with F-actin and interplay with the maize actin severing protein, ZmADF3

EF-1 alpha is an abundant eukaryotic protein whose principle: function appears to be to bind aminoacyl-tRNA to the ribosome. However, it is also known that EF-1 alpha from other sources binds both microtubules and microfilaments. We report the expression of Zea mays EF-1 alpha (ZmEF-1 alpha) in bacteria and that this protein has similar actin-binding properties as other EF-1 alpha members. ZmEF-1 alpha bundles actin filaments at low pH (6.5) and inhibits the addition of monomer at both filament ends, possibly as a consequence. ZmEF-1 alpha binds actin filaments at all pH values tested (pH 6.0-8.0), indicating that one actin binding site is not pH sensitive. One of the actin-binding sites was determined to reside within domain I (1-223) of ZmEF-1 alpha, but this domain did not affect the kinetics of polymerisation. We show that the bundling activity of ZmEF-1 alpha is modulated by ZmADF3 a (a Zea mays ADF/ cofilin), an actin filament severing protein, in vitro. Bundling of actin filaments caused by ZmEF-1 alpha was enhanced in the presence of ZmADF3. The pH-dependent activities of both proteins in vitro suggests that they may work together to respond to temporal and spatial intracellular pH changes to regulate the pattern of the growth of plant cells. Cell Motil. Cytoskeleton 49:103-111, 2001. (C) 2001 Wiley-Liss, Inc.