ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The backbone and side-chain conformations of the bicyclic octapeptide α-amanitin indimethylsulfoxide (DMSO) solution have ben deduced from analysis of the nmr spectrl parameters and conformational energy calculations. Several ambiguities in the nmr spectral assignments were resolved following a comparison with the recently published conformation of β-amanitin in the crystalline state. The peptide proton exchange and temperature coefficient data demonstrate strong intramolecular hyfrogen bonds for the GLY5 and Cys8 peptide protons. The vicinal proton coupling constants are consistent with the cyclic octapeptide udergoing chain reversl at the Ile6-Gly7 abd the Hyp2-Hyi3 dipeptide segments. The upfield shifts of the glycine and isoleucine protons demonstrate the folding of the indole ring of the Trp4-Cys8 brifge towards the Gly5-Ile6-Gly7 half of the Ile-amanitin molecule. The structure af α-amanitin in DMSO is defined by the (φψ) backbone rotation angles Trp4(-90, -60), Gly5 (+120, -120), Ile6(-6, +120), Gly7 (+45, +60), Cys8(-120, -60), Asn1 (+175, -175), Hyp2 (-160, -45), and Hyi3 (-90, -60). The study demonstrates that the structure of α-amanitin in solution is similar to the structure f β-amanitin in the crystalline state.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1978.360170812
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