Characterization of the R and M platelet GPV proteins. (A) Comparison of the H, R, and M GPV amino acid sequences. The amino acid sequences of R and M GPV were deduced from their genes and aligned with the human sequence using CLUSTAL software. Amino acid differences with respect to the human protein are indicated. Residues encoding the signal peptide (SP) and transmembrane domain (TM) are indicated with an overline. Tandem Leu-rich (LR) motifs of 24 amino acids are marked and numbered successively. The Leu-rich boundaries have been modified as compared with Lanza16 to account for the crystal structure of another member of the Leu-rich family, the porcine RNAse inhibitor.36 Each Leu-rich motif starts at the well conserved putative β-strand segment. Potential N-glycosylation sites are underlined. A putative thrombin cleavage site is indicated by a closed arrowhead. (B) Presence of a thrombin cleavage site in R and M GPV. The putative thrombin recognition motif of M GPV is aligned with the H thrombin receptor (TR) cleavage site, while the R GPV motif is compared with the H GPV and H Aα fibrinogen (FgAα) cleavage sites. Identical residues are boxed.