*** 9514790 Beckendorf Cytoplasmic protein tyrosine kinases related to Src constitute a large and growing family involved in many signal transduction pathways. All are confined to the cytoplasm and most are associated with the inner face of the plasma membrane. They typically interact with the cytoplasmic portion of transmembrane receptors, and their kinases activity is stimulated by binding of ligands to the receptors. The activity of Src-family kinases is under tight control so that they are inactive until stimulated. The importance of this regulation is shown by the mutations in Src and several other members of this family that result in constitutive kinase activity and oncogenic transformations. A recently defined subfamily of Src-related kinases includes three mammalian genes, btk, itk and tec, that are all expressed in mammalian hematopoietic cells, and the Drosophila gene Src29A. These genes are lacking the D-terminal tyrosine that negatively regulates most Src-family kinases. They also lack an N-terminal myristylation site that anchors other members of the family to the plasma membrane. In its place members of the subfamily have an extended region of N-terminal homology that implies interactions with other proteins. Because of these structural differences members of this subfamily are likely to be functionally distinct from the previously characterized Src-family kinases, perhaps participating in different signaling pathways or at different levels in familiar pathways. Although Src29A was identified over ten years ago, little is known about its function. It is, however, highly expressed in hematopoietic cells as are its mammalian counterparts. This project seeks to study Src29A function by analyzing zygotic and maternal phenotypes of Src29A! mutants. Dr. Beckendorf has recently identified several P element inserts that inactivate Src29A and have shown that the gene is required for head development. Now he will examine the maternal effects of these mutations and attempt to determin e which signal transduction pathway requires this tyrosine kinase. ***
