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Src homology 2 (SH2) domain found in SH2 adaptor proteins A (SHA) Signal transducers Signal transducing adaptor proteins are accessory to main proteins in a signal transduction pathway. These proteins lack intrinsic enzymatic activity, but mediate specific protein-protein interactions that drive the formation of protein complexes. Adaptor proteins usually contain several domains within their structure (e.g. SH2 and SH3 domains) which allow specific interactions with several other specific proteins. Not much is known about the SHA protein except that it is predicted to act as a transcription factor. Arabidopsis SHA pulled down a 120-kD tyrosine-phosphorylated protein in vitro. In addition to the SH2 domain there is a coiled-coil domain, a DNA binding domain, and a transactivation domain in the STAT proteins. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.
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