Structure of rhodocetin reveals noncovalently bound heterodimer interface

Abstract

Rhodocetin is a unique heterodimer consisting of α- and β-subunits of 133 and 129 residues, respectively. The molecule, purified from the crude venom of the Malayan pit viper, Calloselasma rhodostoma, functions as an inhibitor of collagen-induced aggregation. Rhodocetin has been shown to have activity only when present as a dimer. The dimer is formed without an intersubunit disulfide bridge, unlike all the other Ca2+- dependent lectin-like proteins. We report here the 1.9 Å resolution structure of rhodocetin, which reveals the compensatory interactions that occur in the absence of the disulfide bridge to preserve activity.