Molecular cloning and chromosomal localization of the human homologue of a B-lymphocyte specific protein tyrosine kinase (blk).

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.