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Publication Abstract from PubMed

The cyclotides are the family of hydrophobic bioactive plant peptides, characterized by a circular protein backbone and three knot forming disulfide bonds. It is believed that membrane activity of the cyclotides underlines their antimicrobial, cytotoxic and hemolytic properties, but the specific interactions with divalent cations can be also involved. To assess the mode of membrane interaction and divalent cation coordination in cyclotides, the spatial structure of the Mobius cyclotide Kalata B7 from the African perennial plant Oldenlandia affinis was determined in the presence of anisotropic membrane mimetic (dodecylphosphocholine micelles). The model of peptide/cation/micelle complex was built using 5-doxylstearate and Mn(2+) relaxation probes. Results show that the peptide binds to the micelle surface with relatively high affinity by two hydrophobic loops (loop 2 - Thr(6)-Leu(7) and loop 5 - Trp(19)-Ile(21)). The partially hydrated divalent cation is coordinated by charged side-chain of Glu(3), aromatic side chain of Tyr(11) and free carbonyls of Thr(4) and Thr(9), and is located in direct contact with the polar head-groups of detergent. The comparison with data about other cyclotides indicates that divalent cation coordination is the invariant property of all cyclotides, but the mode of peptide/membrane interactions is varied. Probably, the specific cation/peptide interactions play a major, but yet not known, role in the biological activity of the cyclotides.

Divalent cation coordination and mode of membrane interaction in cyclotides: NMR spatial structure of ternary complex Kalata B7/Mn(2+)/DPC micelle.,Shenkarev ZO, Nadezhdin KD, Lyukmanova EN, Sobol VA, Skjeldal L, Arseniev AS J Inorg Biochem. 2008 Jan 21;. PMID:18295894^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.