| 1. |
- Broussalis, Adriana M., et al.
(författare)
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First cyclotide from Hybanthus (Violaceae)
- 2001
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Ingår i: Phytochemistry. - : Elsevier. - 0031-9422 .- 1873-3700. ; 58:1, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- Hypa A, a novel macrocyclic polypeptide containing 30 amino acid residues, has been isolated from the n-butanol extract of the Argentine plant Hybanthus parviflorus. The sequence, cyclo-(SCVYIPCTITALLGCSCKNKVCYNGIPCAE), was determined by automated Edman degradation, quantitative amino acid analysis and nanospray MS/MS2. Three intramolecular disulfide bridges stabilize the cyclic peptide backbone of hypa A. Using these structural features to classify the peptide as a cyclotide, we extended the distribution of that substance class to a new genus, and now propose a uniform nomenclature for cyclotides.
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| 2. |
- Göransson, Ulf, et al.
(författare)
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Expression of Viola cyclotides by liquid chromatography-mass spectrometry and tandem mass spectrometry sequencing of intercysteine loops after introduction of charges and cleavage sites by aminoethylation
- 2003
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Ingår i: Analytical Biochemistry. - 0003-2697 .- 1096-0309. ; 318:1, s. 107-117
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Tidskriftsartikel (refereegranskat)abstract
- The expression of cyclotides—macrocyclic plant peptides—was profiled in six violets, Viola cotyledon, V. biflora, V. arvensis,V. tricolor, V. riviniana, and V. odorata, by LC-MS. All were found to express notably complex mixtures, with single speciescontaining >50 cyclotides. To facilitate their sequencing by MS-MS, an analytical strategy is presented involving aminoethylation ofcysteines. This overcomes a number of problems intimately associated with the cyclotide core structure—that is, their joined N and Ctermini, disulfide knot, and low or clustered content of positively charged amino acids and enzymatic cleavage sites. As a result,charges as well as cleavage sites are introduced at the most conserved part of their sequence, the cysteines. Combined with trypticdigestion, all intercysteine loops are then of suitable size and charge for MS-MS sequencing. The utility of this strategy is shown bythe sequencing of two novel cyclotides isolated from V. cotyledon; vico A (cyclo-(AESCVYIPCFTGIAGCSCKNKVCYYNGSIPC)) and vico B(cyclo-(AESCVYIPCITGIAGCSCKNKVCYYNGSIPC)); their complete sequence could be determined bynanospray MS-MS. The strategy for converting conserved cysteines to enzymatic cleavage sites might also benefit the study of otherpeptides and proteins displaying similar structural problems for MS analysis.
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