MOLECULAR-CLONING AND CHROMOSOMAL LOCALIZATION OF THE HUMAN HOMOLOG OF A B-LYMPHOCYTE SPECIFIC PROTEIN-TYROSINE KINASE (BLK)

A cDNA encoding the human homologue of the murine protein tyrosine kin ase, blk, has been cloned from a human B-lymphocyte cDNA library by cr oss-species hybridization using the murine blk cDNA as a probe. The se quence of the 2608 bp human blk cDNA clone contains an open reading fr ame encoding a predicted 505 amino acid protein with SH3, SH2 and cata lytic domains that contain consensus sequences of the src protein tyro sine kinase family. Comparison of human and murine blk sequences indic ated that they share 86% amino acid identity, the most conserved regio n 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.