Cloning of a SH3 Domain-Containing Proline-Rich Protein, p85SPR, and Its Localization in Focal Adhesion

Abstract

A mouse thymus cDNA expression library was screened with monoclonal antibody (mAb), B16-5 which binds to common epitope in SH3 domains of phospholipase C-gamma 1 (PLC-gamma 1) and Nck. We have determined the complete nucleotide sequence of one of several positive clones. The 4,172 bp cDNA clone (GenBank Accession No. U96634) encodes a SH3 domain-containing protein of 646 amino acids. Besides the SH3 domain, the predicted 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 distributed in rat tissue with an especially high level of expression in brain and testis. Interestingly, the specific antibodies detected four 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.