1znu

From Proteopedia

Revision as of 05:26, 21 November 2007

Structure of cyclotide Kalata B1 in DPC micelles solution

Overview

Cyclotides are a family of bioactive plant peptides that are characterized, by a circular protein backbone and three conserved tightly packed, disulfide bonds. The antimicrobial and hemolytic properties of cyclotides, along with the relative hydrophobicity of the peptides, point to the, biological membrane as a target for cyclotides. To assess the, membrane-induced conformation and orientation of cyclotides, the, interaction of the Mobius cyclotide, kalata B1, from the African perennial, plant Oldenlandia affinis, with dodecylphosphocholine micelles was studied, using NMR spectroscopy. Under conditions where the cyclotide formed a, well-defined complex with micelles, the spatial structure of kalata B1 was, calculated from NOE and J couplings data, and the model for the, peptide-micelle complex was built using 5- and 16-doxylstearate relaxation, probes. The binding of divalent cations to the peptide-micelle complex was, quantified by Mn2+ titration. The results show that the peptide binds to, the micelle surface, with relatively high affinity, via two hydrophobic, loops (loop 5, Trp19-Val21; and loop6, Leu27-Val29). The charged residues, (Glu3 and Arg24), along with the cation-binding site (near Glu3) are, segregated on the other side of the molecule and in contact with polar, head groups of detergent. The spatial structure of kalata B1 is only, slightly changed during incorporation into micelles and represents a, distorted triple-stranded beta-sheet cross-linked by a cystine knot., Detailed structural analysis and comparison with other knottins revealed, structural conservation of the two-disulfide motif in cyclic and acyclic, peptides. The results thus obtained provide the first model for, interaction of cyclotides with membranes and permit consideration of the, cyclotides as membrane-active cationic antimicrobial peptides.

About this Structure

1ZNU is a Single protein structure of sequence from Oldenlandia affinis. Full crystallographic information is available from OCA.

Reference

Conformation and mode of membrane interaction in cyclotides. Spatial structure of kalata B1 bound to a dodecylphosphocholine micelle., Shenkarev ZO, Nadezhdin KD, Sobol VA, Sobol AG, Skjeldal L, Arseniev AS, FEBS J. 2006 Jun;273(12):2658-72. PMID:16817894

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