Electronic Resource
New York, NY
:
Wiley-Blackwell
Proteins: Structure, Function, and Genetics
10 (1991), S. 251-259
ISSN:
0887-3585
Keywords:
Ricin A-chain
;
x-ray structure
;
active site
;
conserved residues
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
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.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prot.340100309
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