title: Crystallization of ricin A chain obtained from a cloned gene expressed in Escherichia coli.
abstract: Ricin is a heterodimeric toxin of the form AB, where B is a lectin which binds cell surfaces, triggering endocytosis. The B chain then aids the A chain in escaping from the endosome. The A chain enzymatically attacks and inactivates ribosomes, thereby killing the intoxicated cell. We have recently solved the three-dimensional structure of whole ricin. Here we report that the A chain, expressed from a gene cloned into Escherichia coli has been crystallized in a suitable form for high resolution x-ray analysis. The crystals are monoclinic space group P2(1) with a = 42.6, b = 68.1, c = 50.2 A and beta = 112.9 degrees. There is evidence that the A chain undergoes a conformational change, resulting in activation, when it is released from the B chain. Comparison of the two structures should facilitate an analysis of this process.
mesh_terms: D003460:Crystallization; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000235:genetics; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D012276:Ricin / Q000235:genetics
chemical_list: D004274:DNA, Recombinant; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D012276:Ricin