Human homologs of the Xenopus oocyte cortical granule lectin XL35

The cDNAs encoding two human homologs of the Xenopus,us oocyte lectin, XL35 , were isolated from a small intestine cDNA library and termed HL-1 and HL- 2, The deduced amino acid sequence of each homolog is about 60% identical a nd 80% similar to that of XL35, and none of these sequences contains the C- type lectin motif, although it is known that XL35 requires calcium for liga nd binding. By Northern analysis, HL-1 transcripts are present at relativel y high levels in heart, small intestine, colon, thymus, ovary, and testis, HL-2 transcripts, by contrast, are expressed only in small intestine. Immur aocytochemistry using a polyclonal antibody produced against XL35 shows HL- 1 protein to be localized exclusively in endothelial cells in colon, thymus , liver, and other tissues. Primary cultures of human aortic endothelial ce lls are positive for HL-1 expression by immunoblotting and by PCR analysis, but several other human cell types are not. HL-1 and -2 are both encoded a t chromosome 1q23, the same locus that encodes the selectins, XL35, HL-1 an d -2, and another mouse homolog are members of a new family of proteins who se members most likely perform diverse functions.