Selective membrane disruption by the cyclotide kalata B7: complex ions and essential functional groups in the phosphatidylethanolamine binding pocket.

The cyclic cystine knot plant peptides called cyclotides are active against a wide variety of organisms. This is primarily achieved through membrane binding and disruption, in part deriving from a high affinity for phosphatidylethanolamine (PE) lipids. Some cyclotides, such as kalata B7 (kB7), form complexes with divalent cations in a pocket associated with the tyrosine residue at position 15 (Tyr15).

Solubility of recombinant Src homology 2 domains expressed in E. coli can be predicted by TANGO.

Background: Signalling proteins often contain several well defined and conserved protein domains. Structural analyses of such domains by nuclear magnetic spectroscopy or X-ray crystallography may greatly inform the function of proteins. A limiting step is often the production of sufficient amounts of the recombinant protein.

Inhibition of sorbitol dehydrogenase by nucleosides and nucleotides.

Sorbitol dehydrogenase inhibitors have been found to prevent, or alleviate, various secondary complications of diabetes mellitus. In the present study, the effects of nucleosides and nucleotides on the rate of sorbitol oxidation catalyzed by the sheep liver enzyme were studied by steady-state kinetics at pH 7.4.

Cyclic peptides from Oldenlandia affinis DC. Molecular and biological properties.

A new isolation procedure for Kalata polypeptides from the tropical plant Oldenlandia affinis DC is described. Fractions were screened by thin-layer chromatography, and Van Urk positive fractions were tested for oxytocic activity in estrogenized rat uteri. By using this procedure, we were able to isolate and characterize three macrocyclic polypeptides with uterine activity.

Divalent cation coordination and mode of membrane interaction in cyclotides: NMR spatial structure of ternary complex Kalata B7/Mn2+/DPC micelle.

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 Möbius cyclotide Kalata B7 from the African perennial plant Oldenlandia affinis was determined in the presence of anisotropic membrane mimetic (dodecylphosphocholine micelles).