title: The three-dimensional structure of ricin at 2.8 A.
abstract: The x-ray crystallographic structure of the heterodimeric plant toxin ricin has been determined at 2.8-A resolution. The A chain enzyme is a globular protein with extensive secondary structure and a reasonably prominent cleft assumed to be the active site. The B chain lectin folds into two topologically similar domains, each binding lactose in a shallow cleft. In each site a glutamine residue forms a hydrogen bond to the OH-4 of galactose, accounting for the epimerimic specificity of binding. The interface between the A and B chains shows some hydrophobic contacts in which proline and phenylalanine side chains play a prominent role.
mesh_terms: D005690:Galactose / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D012276:Ricin; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D012276:Ricin; D005690:Galactose