Comparison of 1L4a cDNA with members of the Btk family of PTK. (A) Schematic representation of 1L4a cDNA. Structure of 1L4a cDNA was drawn in accordance with the sequence of the 5′ RACE and the cDNA library clones. Lines and boxes represent the UTRs and ORF, respectively. Names of the protein domains encoded by the cDNA are indicated below. Homology with murine Btk and human Bmx is shown for each domain as % of identity at the bp and aa levels. (B) Alignment of the amino-acid sequences of 1L4a cDNA, human Bmx, murine Btk, Tsk, and Tec. Gaps (-) have been introduced for optimal alignment. The different protein domains have been framed. Arrows show partial repeat of the SH3 domain in human Bmx. Potentially phosphorylated tyrosines 194 and 542 are indicated with #.