Amino acid residues in human FVa that contribute to PS binding. The structure of bovine FVa_i solved by Adams et al³⁸  is shown as rendered by the Cn3D software package.⁵¹  Selected amino acids are labeled using the corresponding residues in human FVa. Amino acid residues previously implicated in FVa binding to PS membranes are highlighted in yellow. The indole side chains of Trp²⁰⁶³ and Trp²⁰⁶⁴, located in the FVa C2 domain, penetrate the lipid bilayer and contribute a majority of the free energy associated with FVa binding to PS membranes.²¹  The hydrophobic side chains of Tyr¹⁹⁵⁶ and Leu¹⁹⁵⁷ are located in a structurally analogous position within the FVa C1 domain and provide a modest contribution to the free energy associated with FVa binding to PS membranes.²³  Glycosylation of Asn²¹⁸¹ (green) results in the FVa₁ glycoform. FVa₂ is not glycosylated at Asn²¹⁸¹.