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Structure of ricin A‐chain at 2.5 Å
Author(s) -
Katzin Betsy J.,
Collins Edward J.,
Robertus Jon D.
Publication year - 1991
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340100309
Subject(s) - ricin , chemistry , folding (dsp implementation) , stereochemistry , active site , intramolecular force , molecule , residue (chemistry) , amino acid , biochemistry , biophysics , toxin , biology , enzyme , organic chemistry , electrical engineering , engineering
Ricin has been refined in a crystallographic sense to 2.5 Å resolution and the model for the A‐chain (RTA) is described in detail. Because RTA is the first member of the class of plant toxins to be analyzed, this model probably defines the major structural characteristics of the entire family of these medically important proteins. Explanations are provided to rationalize amino acids that are conserved between RTA and a number of homologous plant and bacterial toxins. Eight invariant residues appear to be involved in creating or stabilizing the active site. In the active site Arg180 and Glu177 are hydrogen bonded to each other and also coordinate a water molecule; each of these groups may be important in the N‐glycosidation reaction. Several other polar residues may play lesser roles in the mechanism, including tyrosines 80 and 123 and asparagines 78 and 209. A number of conserved hydrophobic residues are seen to cluster within several patches and probably drive the overall folding of the toxin molecule.