CLONING AND CHARACTERIZATION OF THE GENE ENCODING THE HUMAN PLATELET GLYCOPROTEIN-V - A MEMBER OF THE LEUCINE-RICH GLYCOPROTEIN FAMILY CLEAVED DURING THROMBIN-INDUCED PLATELET ACTIVATION

Glycoprotein V (GPV) is a major platelet membrane 82-kDa glycoprotein, missing in the Bernard-Soulier syndrome, that is cleaved when platele ts are treated with thrombin. We report the cloning and sequencing of the GPV cDNA and gene obtained by a combination of polymerase chain re action amplification of platelet mRNA and genomic library screening. T he single-copy gene for GPV is contained within 6.5 kilobase pairs (kb ) of genomic sequence and has a simple structure with a single intron of 958 base pairs in the 5'-untranslated sequence; the coding sequence is contained within a single exon. The promoter region contains a can onical TATA box, and putative GATA, Ets-1, and Sp1 cis-acting elements . Reverse transcription-polymerase chain reaction analysis on RNAs fro m cells of different hematopoietic origins revealed that GPV was speci fically transcribed from platelets and from cells of the megakaryocyti c lineage (megakaryocytes, HEL cells). A single transcript of 4.5 kb f or GPV was detected in human platelets by Northern blot analysis. The entire amino acid sequence of GPV was deduced from the cDNA and genomi c sequences. Mature GPV was composed of 544 amino acids which containe d a single transmembrane domain, a short cytoplasmic domain (16 residu es), and a large extracellular domain with 8 potential N-glycosylation sites. Analysis of the extracellular domain revealed the presence of 15 tandem Leu-rich repeats of 24 amino acids with homology to GPIbalph a and identified a cleavage site for thrombin near the COOH terminus w ith similarity to the Aalpha chain of fibrinogen, but no hirudin-like sequence was found.