1df6
From Proteopedia
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1H NMR SOLUTION STRUCTURE OF CYCLOVIOLACIN O1
Overview
Several macrocyclic peptides ( approximately 30 amino acids), with diverse, biological activities, have been isolated from the Rubiaceae and Violaceae, plant families over recent years. We have significantly expanded the range, of known macrocyclic peptides with the discovery of 16 novel peptides from, extracts of Viola hederaceae, Viola odorata and Oldenlandia affinis. The, Viola plants had not previously been examined for these peptides and thus, represent novel species in which these unusual macrocyclic peptides are, produced. Further, we have determined the three-dimensional structure of, one of these novel peptides, cycloviolacin O1, using (1)H NMR, spectroscopy. The structure consists of a distorted triple-stranded, beta-sheet and a cystine-knot arrangement of the disulfide bonds. This, structure is similar to kalata B1 and circulin A, the only two macrocyclic, peptides for which a structure was available, suggesting that despite the, sequence variation throughout the peptides they form a family in which the, overall fold is conserved. We refer to these peptides as the cyclotide, family and their embedded topology as the cyclic cystine knot (CCK) motif., The unique cyclic and knotted nature of these molecules makes them a, fascinating example of topologically complex proteins. Examination of the, sequences reveals they can be separated into two subfamilies, one of which, tends to contain a larger number of positively charged residues and has a, bracelet-like circularization of the backbone. The second subfamily, contains a backbone twist due to a cis-Pro peptide bond and may, conceptually be regarded as a molecular Moebius strip. Here we define the, structural features of the two apparent subfamilies of the CCK peptides, which may be significant for the likely defense related role of these, peptides within plants.
About this Structure
1DF6 is a Single protein structure of sequence from Viola odorata. Full crystallographic information is available from OCA.
Reference
Plant cyclotides: A unique family of cyclic and knotted proteins that defines the cyclic cystine knot structural motif., Craik DJ, Daly NL, Bond T, Waine C, J Mol Biol. 1999 Dec 17;294(5):1327-36. PMID:10600388
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