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展开区分霍乱弧菌细胞溶素前体与其毒素成熟形式。

Unfolding distinguishes the Vibrio cholerae cytolysin precursor from the mature form of the toxin.

机构信息

Indian Institute of Science Education and Research Mohali, Transit Campus: MGSIPAP Complex, Sector 26, Chandigarh 160019, India.

出版信息

Biochemistry. 2011 May 17;50(19):3936-45. doi: 10.1021/bi200332g. Epub 2011 Apr 25.

Abstract

Vibrio cholerae cytolysin (VCC) is a potent cytolytic toxin that induces colloid osmotic lysis of its target eukaryotic cells by forming transmembrane oligomeric β-barrel channels. VCC is secreted by the bacteria as an inactive precursor (Pro-VCC) and is subsequently activated by proteolytic removal of an N-terminal "Pro-domain", thus generating the active form of the toxin (Mature-VCC). Earlier studies have indicated an intramolecular chaperone-like role of the Pro-domain favoring efficient secretion of the toxin from the periplasm into the extracellular space. However, the exact role of the Pro-domain in the VCC structure--function mechanism remains unclear. Here, we have compared the Pro-VCC and Mature-VCC molecules in terms of their structural and conformational properties. We have studied unfolding of the two variants of the VCC molecule in response to an array of denaturing conditions, including low-pH, chemical denaturant and heat-induced unfolding. Pro-VCC shows a more profound tendency to unfold in response to such denaturing conditions compared to Mature-VCC. Biophysical characterization of the isolated Pro-domain further suggests that the increased unfolding propensity of Pro-VCC does not arise because of an increased level of unfolding of the Pro-region itself. Altogether, our results imply that a natively folded architecture of the Pro-VCC molecule with sufficient structural and conformational plasticity presumably allows it to adopt a suitable configuration that is possibly required for its efficient secretion and subsequent proteolytic maturation under physiological conditions.

摘要

霍乱弧菌细胞溶素 (VCC) 是一种有效的细胞溶解毒素,通过形成跨膜寡聚β-桶状通道诱导靶真核细胞的胶体渗透压溶解。VCC 作为无活性前体 (Pro-VCC) 被细菌分泌,并随后通过 N 端“Pro 结构域”的蛋白水解去除而被激活,从而产生毒素的活性形式 (成熟-VCC)。早期的研究表明 Pro 结构域具有分子内伴侣样作用,有利于毒素从周质有效分泌到细胞外空间。然而,Pro 结构域在 VCC 结构-功能机制中的确切作用仍不清楚。在这里,我们比较了 Pro-VCC 和 Mature-VCC 分子在结构和构象特性方面的差异。我们研究了两种 VCC 分子变体对一系列变性条件(包括低 pH 值、化学变性剂和热诱导变性)的折叠情况。与 Mature-VCC 相比,Pro-VCC 对这些变性条件表现出更明显的折叠倾向。对分离的 Pro 结构域的生物物理特性的进一步研究表明,Pro-VCC 折叠倾向增加并不是因为 Pro 区本身的折叠水平增加。总之,我们的结果表明,Pro-VCC 分子的天然折叠结构具有足够的结构和构象可塑性,可能允许它采用一种合适的构象,这可能是其在生理条件下有效分泌和随后蛋白水解成熟所必需的。

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