Mammalian Vav signal transducer protein couples tyrosine kinase signals with the activation of the Rho/Rac GTPases, thus leading to cell differentiation and/or proliferation. We have isolated and characterized the DroVav gene, the homologue of h Vav in Drosophila melanogaster . DroVav encodes a protein (793 residues) whose similarity with hVav is 47 and with hVav2 and hVav3 is 45. DroVav preserves the unique, complex structure of hVav proteins, including the lsquo;calponin homologyrsquo;, dbl homology, pleckstrin homology; SH2 and SH3 domains in addition to regions that are acidic rich, proline rich and cysteine rich. DroVav is located on the X chromosome in polytene interval 18A5;18B and is expressed in all stages of development and in all tissues. In mammalian cells, DroVav is tyrosine-phosphorylated in response to epidermal growth factor receptor (EGFR) induction; in vitro, the DroVav SH2 region is associated with tyrosine-phosphorylated EGFR. Thus, DroVav probably plays a pivotal role as a signal transducer protein during fruit fly development.
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