Liu C F, Tam J P
Department of Microbiology and Immunology, Vanderbilt University, Nashville, TN 37232-2363.
Proc Natl Acad Sci U S A. 1994 Jul 5;91(14):6584-8. doi: 10.1073/pnas.91.14.6584.
We describe the concept and the verification of a chemical ligation approach to the synthesis of proteins using peptide segments with no protecting groups and no activation of the C-terminal alpha-carboxyl group. This approach consists of three steps: (i) aldehyde introduction, in which a masked glycolaldehyde ester is linked to the carboxyl terminus of an unprotected peptide by reverse proteolysis; (ii) ring formation, in which the unmasked aldehyde reacts with the N-terminal alpha-amino group of the second unprotected peptide containing either a cysteine or a threonine residue to form a thiazolidine or oxazolidine ring at an acidic pH; and (iii) rearrangement in which O-acyl ester linkage is transferred to N-acyl amide linkage to form a peptide bond with a pseudoproline structure at higher pH. The feasibility of this scheme was verified by a model study on small compounds and its potential was demonstrated by the synthesis of a 50-residue epidermal growth factor-like peptide containing a preformed disulfide bond.
我们描述了一种化学连接方法的概念及验证，该方法用于合成蛋白质，使用的肽段无保护基团且C端α-羧基未活化。此方法包括三个步骤：（i）醛引入，其中一个掩蔽的乙醇醛酯通过反向蛋白酶解连接到未保护肽的羧基末端；（ii）环化，其中未掩蔽的醛与第二个含有半胱氨酸或苏氨酸残基的未保护肽的N端α-氨基反应，在酸性pH下形成噻唑烷或恶唑烷环；（iii）重排，其中O-酰基酯键转移至N-酰基酰胺键，在较高pH下形成具有假脯氨酸结构的肽键。该方案的可行性通过对小分子化合物的模型研究得到验证，其潜力通过合成含有预先形成的二硫键的50个残基的表皮生长因子样肽得以证明。
