SUBSTRATE RECOGNITION BY RIBOSOME-INACTIVATING PROTEIN STUDIED BY MOLECULAR MODELING AND MOLECULAR ELECTROSTATIC POTENTIALS

A computer model of dianthin 30, a type I ribosome-inactivating protei n (RIP), is constructed by homology modeling using two known X-ray str uctures; a type 1 RIP, pokeweed antiviral protein (PAP), and chain A o f a type 2 RIP, ricin. The 30 structure is refined by molecular dynami cs and its binding site compared with those of PAP and ricin using mol ecular electrostatic potential mapping. The differences in the maps ob tained clearly show how, despite the similarity of the topology of the binding site, differences in electrostatic potential can account for the experimentally observed differences in substrate recognition and b inding. This demonstrates the potential of these techniques for guidin g further experimental analyses.