Structurally relevant amino acid residues are indicated by purple boxes. Cysteine residues, all conserved, are indicated by yellow boxes. All other conserved residues are indicated by asterisks. Canonical VWFA1 domain includes residues 497-716 (1260-1479). The portion of domain D3 on the amino-terminal side was expressed to obtain secreted dimers. In the recombinant GPIbα amino-terminal fragment, unpaired Cys65 was mutated to Ala to avoid dimerization after secretion.