Free-radical-based, specific desulfurization of cysteine: A powerful advance in the synthesis of polypeptides and glycopolypeptides
Free-radical-based, specific desulfurization of cysteine: A powerful advance in the synthesis of polypeptides and glycopolypeptides
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DOI：
10.1002/anie.200704195
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Danishefsky, Samuel J.
中科院分区：
文献类型：
--
作者：
Wan, Qian;Danishefsky, Samuel J.
糖蛋白合成的收敛策略需要组装各个肽基底物，每个底物具有单个碳水化合物结构域。然后，这些亚基将以迭代的方式合并，以最终提供同质的、多糖基化的肽或蛋白质靶。肯特及其同事开发的基于半胱氨酸的天然化学连接（NCL）方案（图1a），[1]遵循肯普等人的早期可行性论证，[2]涉及C-末端硫酯和N-末端半胱氨酸残基的合并。NCL在肽合成方面取得了重大进展，并成为许多进一步研究的起点，包括我们自己的研究。[3]因此，如图1 B所示，我们开发了一种新的NCL变体，其允许通过使用相对惰性的C-末端邻-硫酚酯合并糖肽，所述糖肽带有O-或N-连接的聚糖残基。该基团具有基于半胱氨酸的NCL所需的潜在硫酯官能团。[4]鉴于在许多天然存在的蛋白质和糖蛋白中半胱氨酸残基的相对稀缺性，能够在非半胱氨酸位点实现相当的连接将是有价值的。因此，已经进行了相当大的努力来开发无半胱氨酸的连接方法。我们最近公开了两种互补的基于非半胱氨酸的连接方案，它们一起提供了通过动力学控制的连接进行迭代NCL的手段。[5]Yan和Dawson首先提出的半胱氨酸依赖性问题的替代解决方案利用了基于半胱氨酸的NCL，并通过Raney镍或Pd/Al 2 O3的作用将以前的N-末端半胱氨酸残基转化为丙氨酸残基（图1c）。[6]从本质上讲，Yan和Dawson提供了一种使用半胱氨酸残基作为更丰富的替代物的方法。
A convergent strategy for glycoprotein synthesis entails the assembly of individual peptidyl substrates, each bearing a single carbohydrate domain. These subunits would then be merged, in an iterative fashion, to ultimately afford the homogeneous, multiply glycosylated peptide or protein target. The cysteine-based native chemical ligation (NCL) protocol developed by Kent and co-workers (Figure 1 a),[1] following earlier feasibility demonstrations by Kemp et al.,[2] involves the merger of a C-terminal thioester and an N-terminal cysteine residue. NCL provided a major advance in peptide synthesis, and has served as a launching point for many further investigations, including our own.[3] Thus, as outlined in Figure 1 b, we had developed a novel NCL variant which allows for the merger of glycopeptides, which bear either O-or N-linked glycan residues, through the use of a relatively inert C-terminal ortho-thiophenolic ester. This group harbors the latent thioester functionality required for cysteine-based NCL.[4] In light of the relative scarcity of cysteine residues in many naturally occurring proteins and glycoproteins, it would be valuable to be able to achieve comparable ligations at non-cysteine sites. As such, considerable effort has been addressed to the development of cysteine-free ligation methods. We recently disclosed two complementary non-cysteine-based ligation protocols which together provide a means by which to perform iterative NCL through kinetically controlled ligation.[5] An alternative solution to the problem of cysteine dependence, first proposed by Yan and Dawson, took advantage of cysteine-based NCL and converted the erstwhile N-terminal cysteine residue into an alanine residue through the action of either Raney nickel or Pd/Al2O3 (Figure 1 c).[6] In essence, Yan and Dawson had provided a means by which to use cysteine residues as surrogates for more abundant