Putative PS binding sites. We present here the two putative PS binding sites which are proposed based on our lipid contact frequency calculations (Figure 5). A) Putative site 1, including interactions between PS carboxyl and Ca-7, between PS amino and GLA19, and between PS phosphate and Ca-6. B) Putative site 2, including interactions between PS carboxyl and Ca-1, between PS amino and GLA29, and between PS phosphate and GLN10.