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. 2014 Oct 20;115(6):2296–2349. doi: 10.1021/cr5003529

Figure 50.

Figure 50

Streamlined semisyntheses of ubiquitylated histones. (a) Synthesis of H2B-K120ub containing the G76A mutation in ubiquitin. This mutation enables introduction of residue 76 of ubiquitin as a cysteine and subsequent NCL with a ubiquitin α-thioester. Finally, desulfurization converts Cys76 into an alanine residue. (b) Synthesis of H2A-K119ub containing the G76A mutation in ubiquitin. A penicillamine moiety permits NCL at a valine residue. (c) Disulfide-based conjugation of ubiquitin to H2B-K120C. In this approach, the ubiquitin α-thioester is reacted with cysteamine (top) and coupled to histones activated as disulfides (below), thus yielding disulfide-bonded analogues of H2B-K120ub (H2B-K120ubSS).