CLONING OF A SH3 DOMAIN-CONTAINING PROLINE-RICH PROTEIN, P85SPR, AND ITS LOCALIZATION IN FOCAL ADHESION

A mouse thymus cDNA expression library was screened with monoclonal an tibody (mAb), B16-5 which binds to common epitope ill SH3 domains of p hospholipase C-gamma 1 (PLC-gamma 1) and Nck. We have determined the c omplete nucleotide sequence of one of several positive clones, The 4,1 72 bp cDNA clone (Gen-Bank Accession No, U96634) encodes a SH3 domain- containing protein of 646 amino acids. Besides the SH3 domain, the pre dicted protein has a proline-rich region, nuclear localization signals , and leucine zipper motifs, The expressed protein in Sf9 insect cell exhibits a polypeptide of 85 kDa on SDS-PAGE. The protein is widely di stributed in rat tissue with am especially high level of expression in brain and testis. Interestingly, the specific antibodies detected fou r related proteins of different size (75, 85, 90 and 105 kDa) in brain , In A431 cell, p85SPR is enriched at focal adhesion points indicating that the protein may interact with protein(s) in focal complexes. (C) 1997 Academic Press.