1pt4
From Proteopedia
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Solution structure of the Moebius cyclotide kalata B2
Overview
A large number of macrocyclic miniproteins with diverse biological, activities have been isolated from the Rubiaceae, Violaceae, and, Cucurbitaceae plant families in recent years. Here we report the, three-dimensional structure determined using (1)H NMR spectroscopy and, demonstrate potent insecticidal activity for one of these peptides, kalata, B2. This peptide is one of the major components of an extract from the, leaves of the plant Oldenlandia affinis. The structure consists of a, distorted triple-stranded beta-sheet and a cystine knot arrangement of the, disulfide bonds and is similar to those described for other members of the, cyclotide family. The unique cyclic and knotted nature of these molecules, makes them a fascinating example of topologically complex proteins., Examination of the sequences reveals that they can be separated into two, subfamilies, one of which contains 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-peptidyl-proline, bond and may conceptually be regarded as a molecular Mobius strip. Kalata, B2 is the second putative member of the Mobius cyclotide family to be, structurally characterized and has a cis-peptidyl-proline bond, thus, validating the suggested name for this subfamily of cyclotides. The, observation that kalata B2 inhibits the growth and development of, Helicoverpa armigera larvae suggests a role for the cyclotides in plant, defense. A comparison of the sequences and structures of kalata B1 and B2, provides insight into the biological activity of these peptides.
About this Structure
1PT4 is a Single protein structure of sequence from Oldenlandia affinis. Full crystallographic information is available from OCA.
Reference
Isolation, solution structure, and insecticidal activity of kalata B2, a circular protein with a twist: do Mobius strips exist in nature?, Jennings CV, Rosengren KJ, Daly NL, Plan M, Stevens J, Scanlon MJ, Waine C, Norman DG, Anderson MA, Craik DJ, Biochemistry. 2005 Jan 25;44(3):851-60. PMID:15654741
Page seeded by OCA on Wed Nov 21 00:06:10 2007
