Methionine ligation strategy in the biomimetic synthesis of parathyroid hormones.
Methionine ligation strategy in the biomimetic synthesis of parathyroid hormones.
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DOI：
10.1002/(sici)1097-0282(19981015)46:5
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发表时间：
1998-10
期刊：
影响因子：
2.9
通讯作者：
J. Tam;Q. Yu
中科院分区：
文献类型：
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作者：
J. Tam;Q. Yu
在生物系统中，酰胺键的蛋白水解和氨水解都通过分子间或分子内的酰基转移反应产生活化的中间体。蛋白质剪接是一个说明性的例子，它通过一系列催化酰基转移反应进行，并在O-或s -酰基中间达到高潮。这种中间体导致未催化的酰基迁移，在剪接产物中形成酰胺键。利用酰基转移酰胺键特征，将蛋氨酸（Met）上无保护的游离肽段进行块状偶联，开发了一种模拟蛋白质剪接中未催化的最后步骤的连接方法。利用游离肽α -氨基末端的同型半胱氨酸，可以利用Met的潜伏巯基部分与含有α -巯基的另一游离肽进行转硫酯化反应，得到s -酰基中间体。随后，这种酰基中间体的邻近驱动的S-到n -酰基迁移自发重排形成同型半胱氨酸酰胺键。与过量对硝基苯磺酸的s甲基化在连接部位产生Met。蛋氨酸连接具有选择性和正交性，在弱碱性pH和强还原条件下，通常在4小时内完成。在甲状旁腺激素肽的合成中，没有观察到由于酰化而与任何其他肽段的α胺发生的副反应。此外，也可以通过相同的策略，在无保护的肽前体中，将同型半胱氨酸置于氨基端，将硫酯置于羧基端，从而获得环肽。这些仿生连接策略有望用于工程新型肽和蛋白质。
In biological systems, both proteolysis and aminolysis of amide bonds produce activated intermediates through acyl transfer reactions either inter- or intramolecularly. Protein splicing is an illustrative example that proceeds through a series of catalyzed acyl transfer reactions and culminates at an O- or S-acyl intermediate. This intermediate leads to an uncatalyzed acyl migration to form an amide bond in the spliced product. A ligation method mimicking the uncatalyzed final steps in protein splicing has been developed utilizing the acyl transfer amide-bond feature for the blockwise coupling of unprotected, free peptide segments at methionine (Met). The latent thiol moiety of Met can be exploited using homocysteine at the alpha-amino terminal position of a free peptide for transthioesterification with another free peptide containing an alpha-thioester to give an S-acyl intermediate. A subsequent, proximity-driven S- to N-acyl migration of this acyl intermediate spontaneously rearranges to form a homocysteinyl amide bond. S-methylation with excess p-nitrobenezensulfonate yields Met at the ligation site. The methionine ligation is selective and orthogonal, and is usually completed within 4 h when performed at slightly basis pH and under strongly reductive conditions. No side reactions due to acylation were observed with any other alpha-amines of both peptide segments as seen in the synthesis of parathyroid hormone peptides. Furthermore, cyclic peptide can also be obtained through the same strategy by placing both homocysteine at the amino terminus and the thioester at the carboxyl terminus in an unprotected peptide precursor. These biomimetic ligation strategies hold promise for engineering novel peptides and proteins.