12 パリトキシン分子形状の直接観察 : 放射光X線小角散乱測定による水溶液中配座の研究(口頭発表の部)

概要

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Marine organic metabolites that are composed of a long carbon backbone functionalized by oxygen atoms have been called "super-carbon-chain compounds". To proceed further functional studies of these compounds, we first revealed the whole shape of these molecules in the water solution state, by using palytoxin (PTX). PTX is a marine natural product with a molecular weight of 2680. PTX shows potent toxicity against mice and interacts with Na/K ATPase. Since the acetamide of PTX (NAcPTX) shows reduced pharmacological activity, elucidation of the structures of both PTX and NAcPTX in solution would be interesting from a biological perspective. We solved these structures by using the small angle X-ray scattering (SAXS) technique with an intense synchrotron X-ray source. PTX was found to exist as a dimer, while NAcPTX existed as a monomer. We simulated low-resolution models for PTX and NAcPTX from the SAXS profiles by using a chain-like ensemble of dummy residues modeling methods. The overall shape of NAcPTX in water was horseshoe-like in water, while PTX was prolonged oblate. Interestingly, single-site acetylation at the N-terminus of PTX greatly affect the association of PTX molecules.
2006-09-15