Structural analysis of actinidin and a comparison of cadmium and sulfur anomalous signals from actinidin crystals measured using in-house copper- and chromium-anode X-ray sources.

The structure of the 24 kDa cysteine protease saru-actinidin from the fruit of Actinidia arguta Planch. (sarunashi) was determined by the cadmium/sulfur-SAD method with X-ray diffraction data collected using in-house Cu Kα and Cr Kα radiation. The anomalous scatterers included nine sulfurs and several cadmium ions from the crystallization solution. The high quality of the diffraction data, the use of chromium-anode X-ray radiation and the substantial anomalous signal allowed structure determination and automated model building despite both a low solvent content (<40%) and low data multiplicity. The amino-acid sequence of saru-actinidin was deduced from the cDNA and was modified based on experimental electron-density maps at 1.5 Šresolution. The active site of saru-actinidin is occupied by a cadmium ion and the active-site cysteine is found to be in an unmodified, cysteine sulfenic acid or cysteine sulfinic acid form. The cadmium sites, coordination geometries and polygonal water structures on the protein surface have also been extensively analyzed. An analysis and comparison of the sulfur/cadmium anomalous signals at the Cu Kα and Cr Kα wavelengths was carried out. It is proposed that the inclusion of cadmium salts in crystallization solutions coupled with chromium-anode radiation can provide a convenient route for structure determination.

3beta-taraxerol of Mangifera indica, a PI3K dependent dual activator of glucose transport and glycogen synthesis in 3T3-L1 adipocytes.

BACKGROUND: The present study focuses on identifying and developing an anti-diabetic molecule from plant sources that would effectively combat insulin resistance through proper channeling of glucose metabolism involving glucose transport and storage. METHODS: Insulin-stimulated glucose uptake formed the basis for isolation of a bioactive molecule through column chromatography followed by its characterization using NMR and mass spectroscopic analysis. Mechanism of glucose transport and storage was evaluated based on the expression profiling of signaling molecules involved in the process. RESULTS: The study reports (i) the isolation of a bioactive compound 3beta-taraxerol from the ethyl acetate extract (EAE) of the leaves of Mangifera indica (ii) the bioactive compound exhibited insulin-stimulated glucose uptake through translocation and activation of the glucose transporter (GLUT4) in an IRTK and PI3K dependent fashion. (iii) the fate of glucose following insulin-stimulated glucose uptake was ascertained through glycogen synthesis assay that involved the activation of PKB and suppression of GSK3beta. GENERAL SIGNIFICANCE: This study demonstrates the dual activity of 3beta-taraxerol and the ethyl acetate extract of Mangifera indica as a glucose transport activator and stimulator of glycogen synthesis. 3beta-taraxerol can be validated as a potent candidate for managing the hyperglycemic state.