THE SOLUTION STRUCTURE OF TYPE-II ANTIFREEZE PROTEIN REVEALS A NEW MEMBER OF THE LECTIN FAMILY

A recombinant form of the sea raven type II antifreeze protein (SRAFP) has been produced using the Pichia pastoris expression system. The an tifreeze activity of recombinant SRAFP is indistinguishable from that of the wild-type protein. The global fold of SRAFP has been determined by two-dimensional H-1 homonuclear and three-dimensional H-1-{N-15} h eteronuclear NMR spectroscopy using 785 NOE distance restraints and 47 angular restraints. The molecule folds into one globular domain that consists of two helices and nine beta-strands in two beta-sheets. The structure confirms the proposed existence of five disulfide bonds. The global fold of SRAFP is homologous to C-type lectins and pancreatic s tone proteins, even though the sequence identity is only approximately 20%.