寄生在鱼类和贝类里的单细胞藻类会产生毒素，人们如果食用了被感染的海产品，就会出现腹泻、麻痹或是神经方面的问题。法国国家科研中心3月10日报告说，法美两国科学家最近发现了两种海鲜毒素的致病机制。
来自法国国家科研中心、法国原子能委员会和美国加利福尼亚大学的研究人员在新一期美国《美国科学院院刊》（PNAS）上介绍说，他们选取两种名为spirolide和gymnodimine的海鲜藻毒素为研究对象，将这两种毒素分别注入实验鼠体内，结果几分钟内，实验鼠就出现了严重的精神紊乱。
研究人员分析发现，藻毒素的攻击对象是一种位于肌肉和神经细胞膜上的接收器。这种名为nrACh的接收器一旦被藻毒素控制，就会导致肌肉和大脑等运行异常。
研究人员说，这一发现将有助于藻毒素解毒药物的研发。自1991年以来，加拿大、挪威、西班牙、突尼斯和法国等多个国家相继发现了被藻毒素感染的海鲜。因此，研发藻毒素解毒药物无论在公共卫生方面还是经济效益方面都至关重要。
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.0912372107
Structural determinants in phycotoxins and AChBP conferring high affinity binding and nicotinic AChR antagonism
Yves Bournea,1, Zoran Radi?b, Rómulo Aráozc, Todd T. Talleyb, Evelyne Benoitc, Denis Serventd, Palmer Taylorb, Jordi Molgóc, and Pascale Marchote,1
Spirolide and gymnodimine macrocyclic imine phycotoxins belong to an emerging class of chemical agents associated with marine algal blooms and shellfish toxicity. Analysis of 13-desmethyl spirolide C and gymnodimine A by binding and voltage-clamp recordings on muscle-type α12βγδ and neuronal α3β2 and α4β2 nicotinic acetylcholine receptors reveals subnanomolar affinities, potent antagonism, and limited subtype selectivity. Their binding to acetylcholine-binding proteins (AChBP), as soluble receptor surrogates, exhibits picomolar affinities governed by diffusion-limited association and slow dissociation, accounting for apparent irreversibility. Crystal structures of the phycotoxins bound to Aplysia-AChBP (≈2.4?) show toxins neatly imbedded within the nest of ar-omatic side chains contributed by loops C and F on opposing faces of the subunit interface, and which in physiological conditions accommodates acetylcholine. The structures also point to three major features: (i) the sequence-conserved loop C envelops the bound toxins to maximize surface complementarity; (ii) hydrogen bonding of the protonated imine nitrogen in the toxins with the carbonyl oxygen of loop C Trp147 tethers the toxin core centered within the pocket; and (iii) the spirolide bis-spiroacetal or gymnodimine tetrahydrofuran and their common cyclohexene-butyrolactone further anchor the toxins in apical and membrane directions, along the subunit interface. In contrast, the se-quence-variable loop F only sparingly contributes contact points to preserve the broad receptor subtype recognition unique to phycotoxins compared with other nicotinic antagonists. These data offer unique means for detecting spiroimine toxins in shellfish and identify distinctive ligands, functional determinants and binding regions for the design of new drugs able to target several receptor subtypes with high affinity.
