A cDNA encoding the human homologue of the murine protein tyrosine kinase, blk, has been cloned from a human B-lymphocyte cDNA library by cross-species hybridization using the murine blk cDNA as a ...probe. The sequence of the 2608 bp human blk cDNA clone contains an open reading frame encoding a predicted 505 amino acid protein with SH3, SH2 and catalytic domains that contain consensus sequences of the src protein tyrosine kinase family. Comparison of human and murine blk sequences indicated that they share 86% amino acid identity, the most conserved region being the catalytic domain (93% identity). Like the murine blk gene human blk is expressed only in B lymphocytes. The human blk gene was mapped to chromosome 8 at p22-23.
We have studied two anti-p185 antibodies: the monoclonal antibody 7.16.4 and rhuMAb 4D5, which were raised against the the ectodomain of rat (p185neu), and the human (p185her2/neu) homolog, ...respectively. Studies on the structure of these two antibodies indicate that they share structural similarity in the variable region, especially the CDR3 region, which determines the antibody–antigen interaction. Further studies by flow cytometry revealed that 7.16.4 can compete with rhuMAb4D5 for binding to the cell surface p185her2/neu, suggesting that these two antibodies share an epitope on the p185 receptor. Furthermore, 7.16.4 can also inhibit proliferation and transformation caused by p185her2/neu. Moreover the rhuMAb 4D5 binds to the rat p185neu. With the observation that 7.16.4 positively stains human breast cancer tissues that overexpress p185her2/neu, 7.16.4 may be useful for the pathological diagnosis and therapy of human tumors.
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