PRELIMINARY CRYSTALLOGRAPHIC CHARACTERIZATION OF RICIN AGGLUTININ

The quaternary structure of ricin agglutinin (RCA) has been determined by x-ray crystallography. The refined structure of ricin proved to be a successful search model using the molecular replacement method of p hase determination. RCA forms an elongated molecule of dimensions 120 Angstrom x 60 Angstrom, x 40 Angstrom with two A chains at the center and a a chain at each end. The A chains are covalently associated via a disulfide bridge between Cys 156 of both chains. Additional contacts at residues 114-115 stabilize the dimer interface. The covalent assoc iation of RCAA chains tvas confirmed by gel filtration under reducing and nonreducing conditions. (C) 1997 Wiley-Liss, Inc.