Abstract
A new physiological target for Cdc2 protein kinase has been identified. It corresponds to a protein EF-1 delta, a constituent of the nucleotide exchange factor EF-1 beta gamma delta, involved in the elongation step of protein synthesis. EF-1 delta is phosphorylated by Cdc2 kinase on threonine and serine residues. Threonine has been identified as Thr122 in the sequence VQVTPAAK. During oocyte maturation, Thr122 is phosphorylated at metaphase, when p34cdc2 is active. Phosphorylation studies revealed the presence of two post-translational regulated forms of EF-1 delta protein. Identification of two isoforms of the delta protein, together with the presence of two guanine-nucleotide exchange proteins (beta and delta) and physiologically regulated phosphorylation sites by Cdc2 kinase on gamma and delta proteins, implicate that EF-1 beta gamma delta exists in the cell under a multitude of macromolecular forms which suggests that EF-1 beta gamma delta is a sophisticated regulatory factor rather than a "housekeeping" element of the cell.
Highlights
To cite this version: Odile Mulner-Lorillon, Odile Minella, Patrick Cormier, Jean-Paul Capony, Jean-Claude Cavadore, et al
Anew physiological target CfodrcZ protein kinase has We show here that EF-16 is an in vivo substrate for Cdc2 been identifiedI.t corresponds to a proteEinF-IS, a con- protein kinase
Threonine has been identified as Thr'22 ignrown oocytes from Xenopus laevis were obtained, microinjected, and thesequence VQVTPAAK
Summary
6 protein, together with the presencoef two guanine-nucleotide exchange proteins( p and 6) and physiologically regulated. Asecond silent mutation was parallelly in- (Fig. 1).In metaphase cytosolic fractions, both bands of the troduced at the KpnI restriction siteof the insert, allowing the screen- EF-16 doublet were recognized by the antibodies (Fig. 1, left rineagScoytfinotthnheewtimacsumctoRantNfeiAdrcmsloewndeebsreybyDprrNeepAstarsrieecdqtiuobeynnscmtianangpd(aSarnadmalibynrsvoisiot.rkoTethatreal.n,ms1c9uri8tpa9tg)ie.onnesislaannteib: oMd)i.esIsdpeenctiifcicaalllyredsuirletwsceteredoabgtaaiinnsetd usingaffinity-purified protein (Fig. 1, right protocol (mRNA capping kit, Stratagefnr)om purified pBluescriptKS I1 lane: M). This strongly suggests that the upper band of the phagemid containing nativeor mutated EF-16 cDNA.
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