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首页> 外文期刊>Biochemistry >Folding of ω-Conotoxins. 2. Influence of Precursor Sequences and Protein Bisulfide Isomerase
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Folding of ω-Conotoxins. 2. Influence of Precursor Sequences and Protein Bisulfide Isomerase

机译：ω-芋螺毒素的折叠。 2.前体序列和蛋白质二硫键异构酶的影响

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摘要

The peptide Ca~(2+) channel antagonists found in the venoms of Conus snails. ω-conotoxins, are synthesized as precursors that include a leader peptide, presumed to direct the polypeptide to the endoplasmic reticulum, and a propeptide of unknown function. In addition, the precursors are synthesized with a C-terminal Gly residue that is posttranslationally converted to a terminal amide group. In order to determine whether the precursor sequences contain information that helps direct folding of the mature sequences, the disulfide- coupled folding of mature ω -conotoxin MVIIA was compared with that of two putative precursor forms: pro-ω-MVIlA-Gly, which contains the propeptide and the C-terminal Gly residue, and ω-MVHA-Gly, which differs ftom the mature form only at the C-teiminus. The three forms folded with similar kinetics, but the folding efficiency of ω-MVHA-Gly was greater than 80%, versus approximately 50% for both mature co-MVIIA and the form containing the propeptide. The enzyme protein disulfide isomerase was found to catalyze disulfide formation and folding of all three forms similarly. The affinity of ω-MVIIA-Gly for receptors in chick brain synaptosomes was approximately 10-fold lower than that of the mature peptide, and the N-terminal propeptide of pro-ω-MVIIA-Gly was found to decrease binding further, by approximately 100-fold. These results suggest that the ω-conotoxins do not rely on , the propeptide region of their precursors to facilitate folding. Rather, the mature sequence contains most of the information required to specify the native disulfide pairings and three-dimensional conformation. The C-terminal Gly may enhance the folding efficiency by forming interactions that stabilize the native conformation with respect toother disulfide-bonded forms.
机译：圆锥蜗牛毒液中的Ca〜（2+）通道拮抗剂。 ω-芋螺毒素被合成为包括前导肽的前体，假定该前导肽将多肽引导至内质网以及功能未知的前肽。另外，合成前体具有C末端Gly残基，该残基被翻译后转化为末端酰胺基。为了确定前体序列是否包含有助于指导成熟序列折叠的信息，将成熟的ω-芋螺毒素MVIIA的二硫键折叠与两种假定的前体形式：pro-ω-MVIlA-Gly进行了比较。前肽和C末端的Gly残基以及ω-MVHA-Gly，它们仅在C末端的成熟形式不同。三种形式以相似的动力学折叠，但是ω-MVHA-Gly的折叠效率大于80％，而对于成熟的co-MVIIA和含有前肽的形式，折叠效率均约为50％。发现酶蛋白二硫键异构酶类似地催化所有三种形式的二硫键形成和折叠。 ω-MVIIA-Gly对鸡脑突触体中受体的亲和力比成熟肽低约10倍，并且发现前ω-MVIIA-Gly的N端前肽进一步降低了结合力100倍这些结果表明，ω-芋螺毒素不依赖其前体的前肽区域来促进折叠。而是，成熟序列包含指定天然二硫键配对和三维构象所需的大多数信息。 C端Gly可以通过形成相对于其他二硫键键合形式稳定天然构象的相互作用来增强折叠效率。

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