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首页> 外文期刊>Biochemistry >Hydrophobic amino acids define the carboxylation recognition site in the precursor of the gamma-carboxyglutamic-acid-containing conotoxin epsilon-TxIX from the marine cone snail Conus textile.
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Hydrophobic amino acids define the carboxylation recognition site in the precursor of the gamma-carboxyglutamic-acid-containing conotoxin epsilon-TxIX from the marine cone snail Conus textile.

机译：疏水氨基酸定义了来自海洋蜗牛蜗牛康纳斯纺织公司的含有γ-羧基谷氨酸的conotoxin epsilon-TxIX的前体中的羧化识别位点。

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摘要

To identify the amino acid sequence of the precursor of the Gla-containing peptide, epsilon-TxIX, from the venom of the marine snail Conus textile, the cDNA encoding this peptide was cloned from a C. textile venom duct library. The cDNA of the precursor form of epsilon-TxIX encodes a 67 amino acid precursor peptide, including an N-terminal prepro-region, the mature peptide, and four residues posttranslationally cleaved from the C-terminus. To determine the role of the propeptide in gamma-carboxylation, peptides were designed and synthesized based on the propeptide sequence of the Gla-containing conotoxin epsilon-TxIX and used in assays with the vitamin K-dependent gamma-glutamyl carboxylase from C. textile venom ducts. The mature acarboxy peptide epsilon-TxIX was a high K(M) substrate for the gamma-carboxylase. Synthetic peptides based on the precursor epsilon-TxIX were low K(M) substrates (5 &mgr;M) if the peptides included at least 12 residues of propeptide sequence, from -12 to -1. Leucine-19, leucine-16, asparagine-13, leucine-12, leucine-8 and leucine-4 contribute to the interaction of the pro-conotoxin with carboxylase since their replacement by aspartic acid increased the K(M) of the substrate peptide. Although the Conus propeptide and the propeptides of the mammalian vitamin K-dependent proteins show no obvious sequence homology, synthetic peptides based upon the structure of pro-epsilon-TxIX were intermediate K(M) substrates for the bovine carboxylase. The propeptide of epsilon-TxIX contains significant alpha-helix, as estimated by measurement of the circular dichroism spectra, but the region of the propeptide that plays the dominant role in directing carboxylation does not contain evidence of helical structure. These results indicate that the gamma-carboxylation recognition site is defined by hydrophobic residues in the propeptide of this conotoxin precursor.
机译：为了从海洋蜗牛Conus纺织品的毒液中鉴定含Gla的肽前体epsilon-TxIX的氨基酸序列，从C.纺织品毒液导管文库中克隆了编码该肽的cDNA。 ε-TxIX的前体形式的cDNA编码一个67个氨基酸的前体肽，包括N端前原区，成熟肽和四个从C末端翻译后切割的残基。为了确定前肽在γ-羧化中的作用，基于含Gla的芋螺毒素epsilon-TxIX的前肽序列设计和合成了肽，并将其用于与C.纺织毒液中维生素K依赖的γ-谷氨酰羧化酶一起进行测定管道。成熟的羧基羧基ε-TxIX是γ-羧化酶的高K（M）底物。如果基于前体ε-TxIX的合成肽包含至少12个前肽序列残基（-12至-1），则它们是低K（M）底物（5 mg.M）。亮氨酸19，亮氨酸16，天冬酰胺13，亮氨酸12，亮氨酸8和亮氨酸4有助于促毒素和羧化酶的相互作用，因为它们被天冬氨酸替代增加了底物肽的K（M）。 。尽管Conus前肽和哺乳动物维生素K依赖性蛋白的前肽没有明显的序列同源性，但基于前ε-TxIX结构的合成肽是牛羧化酶的中间K（M）底物。通过测量圆二色性光谱估计，ε-TxIX的前肽含有明显的α-螺旋，但在指导羧化中起主要作用的前肽区域不包含螺旋结构的证据。这些结果表明，γ-羧化识别位点由该芋螺毒素前体的前肽中的疏水残基定义。

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