The cDNAs encoding two forms of the LYN protein tyrosine kinase are expressed in rat mast cells and human myeloid cells.
Two isoforms of lck/yes-related novel (LYN) protein tyrosine kinase (PTK) appear to play a role in B-cell-IgM and FcERI receptor signaling. The cDNAs lynA and lynB encoding these two forms were isolated and sequenced; they were derived from rat mucosal mast cell and human myeloid cell lines. The nucleotide (nt) and deduced amino acid (aa) sequences share 94 and 97% identity between rat and mouse lyn, respectively, and 88 and 96% identity between rat and human lyn. In all three species, a region of 20 aa is uniformly inserted at an identical site and its sequence is highly conserved. This suggests an important regulatory role for this region mediated by this PTK.