1rtc
From Proteopedia
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THE STRUCTURE OF RECOMBINANT RICIN A CHAIN AT 2.3 ANGSTROMS
Overview
The plant cytotoxin ricin is a heterodimer with a cell surface binding (B) chain and an enzymatically active A chain (RTA) known to act as a specific N-glycosidase. RTA must be separated from B chain to attack rRNA. The X-ray structure of ricin has been solved recently; here we report the structure of the isolated A chain expressed from a clone in Escherichia coli. This structure of wild-type rRTA has and will continue to serve as the parent compound for difference Fouriers used to assess the structure of site-directed mutants designed to analyze the mechanism of this medically and commercially important toxin. The structure of the recombinant protein, rRTA, is virtually identical to that seen previously for A chain in the heterodimeric toxin. Some minor conformational changes due to interactions with B chain and to crystal packing differences are described. Perhaps the most significant difference is the presence in rRTA of an additional active site water. This molecule is positioned to act as the ultimate nucleophile in the depurination reaction mechanism proposed by Monzingo and Robertus (1992, J. Mol. Biol. 227, 1136-1145).
About this Structure
1RTC is a Single protein structure of sequence from Ricinus communis. Active as rRNA N-glycosylase, with EC number 3.2.2.22 Full crystallographic information is available from OCA.
Reference
Structure of recombinant ricin A chain at 2.3 A., Mlsna D, Monzingo AF, Katzin BJ, Ernst S, Robertus JD, Protein Sci. 1993 Mar;2(3):429-35. PMID:8453380
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