9304469 Shoelson Growth factor/insulin stimulation of the respective tyrosine kinase receptors results in the physical assembly of macromolecular protein complexes at the cytoplasmic surface of the cell membrane. These protein-protein associations are mediated by interactions between phosphoproteins and additional cytoplasmic proteins having Src-homology 2 (SH2) domains (ca.100 residue, modular phosphotyrosine binding pockets). Recently several methods were developed to analyze structure/function relationships between intact phosphoproteins and SH2 domain proteins and truncated versions of both. These findings suggest that phosphoprotein interactions with PI 3-kinase SH2 domains might regulate enzyme function by an allosteric mechanism. This project proposes to extend these observations and determine whether SH2 domain occupancy is a generalized mechanism for regulating catalytic activity. Two members of each SH2 protein class will be analyzed: tyrosine kinases Src & Lck, other enzymes PLC-gamma & SH-PTP, and putative linkers PI 3-kinase p85 & Crk. %%% Many growth factors and related hormones like insulin activate receptors with intrinsic protein tyrosine kinase activity to elicit a wide range of biochemical responses, which ultimately lead to changes in cellular differentiation, metabolism, morphology and proliferation. These studies explore how a class of soluble proteins called SH2 domain proteins contributes to the regulation of signal transduction mediated by these hormones and growth factors. ***
