Jimenez E C, Craig A G, Watkins M, Hillyard D R, Gray W R, Gulyas J, Rivier J E, Cruz L J, Olivera B M
Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines.
Biochemistry. 1997 Feb 4;36(5):989-94. doi: 10.1021/bi962840p.
We demonstrate that post-translational bromination of a tryptophan residue occurs in the biologically active octapeptide bromocontryphan, purified and characterized from Conus radiatus venom. Clones encoding bromocontryphan were identified from a cDNA library made from C. radiatus venom ducts. The mRNA sequence obtained predicts a prepropeptide which has the mature peptide sequence at the C-terminal end, with the L-6-bromotryptophan residue encoded by UGG, the Trp codon. These data provide the first direct evidence for post-translational bromination of a polypeptide which is translated through the normal cellular machinery. In addition to bromination, the peptide, which induces a "stiff tail" syndrome in mice, has several other modifications as shown by the sequence [Formula: See Text] in which Hyp = hydroxyproline. Asterisks indicate post-translational modifications (left to right): proteolytic cleavage at the N-terminus; hydroxylation of Pro3; epimerization of Trp4; bromination of Trp7, and C-terminal amidation. Bromocontryphan appears to have the highest density of post-translational modifications known among gene-encoded polypeptides. The overall result is a molecule which closely resembles marine natural products produced through specialized biosynthetic pathways comprising many enzyme-catalyzed steps.
我们证明，从辐射芋螺毒液中纯化并鉴定出的具有生物活性的八肽溴化芋螺毒素中，色氨酸残基发生了翻译后溴化修饰。从辐射芋螺毒液管构建的cDNA文库中鉴定出了编码溴化芋螺毒素的克隆。获得的mRNA序列预测出一种前体肽，其在C末端具有成熟肽序列，其中L-6-溴色氨酸残基由UGG（色氨酸密码子）编码。这些数据为通过正常细胞机制翻译的多肽的翻译后溴化修饰提供了首个直接证据。除了溴化修饰外，该在小鼠中诱导“硬尾”综合征的肽还有其他几种修饰，如序列[公式：见正文]所示，其中Hyp = 羟脯氨酸。星号表示翻译后修饰（从左至右）：N末端的蛋白水解切割；Pro3的羟化；Trp4的差向异构化；Trp7的溴化以及C末端酰胺化。溴化芋螺毒素似乎在基因编码的多肽中具有已知的最高翻译后修饰密度。总体结果是一个与通过包含许多酶催化步骤的特殊生物合成途径产生的海洋天然产物非常相似的分子。
