ANALYSIS OF SHORTHORN SCULPIN ANTIFREEZE PROTEIN STEREOSPECIFIC BINDING TO (2-10) FACES OF ICE

In this paper we report the results of our studies on the stereospecif ic binding of shorthorn sculpin antifreeze protein (AFP) to (2-10) sec ondary prism faces of ice. Using ice crystal growth and etching techni ques together with molecular modeling, molecular dynamics, and energy minimization, we explain the nature of preferential binding of shortho rn sculpin AFP along the [122] direction on (2-10) planes. In agreemen t with ice etching studies, the mechanism of preferential binding sugg ested by molecular modeling explains why the binding of shorthorn scul pin AFP occurs along [122] and not along its mirror symmetry-related d irection [-1-22] on (2-10). This binding mechanism is based on the pro tein-crystal surface enantioselective recognition that utilizes both a lpha-helical protein backbone matching to the (2-10) surface topograph y and matching of side chains of polar/charged residues with specific water molecule positions in the ice surface. The mechanisms of winter flounder and shorthorn sculpin antifreeze binding to ice re compared.