A mechanistic investigation of the enhanced cleavage at histidine in the gas-phase dissociation of protonated peptides
A mechanistic investigation of the enhanced cleavage at histidine in the gas-phase dissociation of protonated peptides
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DOI：
10.1021/ac034971j
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发表时间：
2004-04-01
影响因子：
7.4
通讯作者：
Wysocki, VH
中科院分区：
文献类型：
--
作者：
Tsaprailis, G;Nair, H;Wysocki, VH
研究了与组氨酸相邻的肽的增强气相裂解。所检查的肽是血管紧张素 III (RVYIHPF) 和 IV (VYIHPF) 以及具有改变的关键残基 ((R)VYI-X-Z-F；X = F 或 H 且 Z = A、P 或 Sar) 或固定电荷 M3P(+)CH(2)C(O)-VYIHPF 的合成肽类似物。虽然所有同时含有组氨酸和精氨酸的单质子化肽离子都会非选择性断裂，但含有精氨酸和组氨酸的双质子化肽离子以及含有组氨酸但不含有精氨酸的单质子化肽会以选择性方式裂解。特别是，观察到 HP 酰胺键之间裂解产生的主要互补 b(+)/y(+) 产物离子。对于固定电荷衍生物，只有在添加质子以产生带双电荷的前体时才会发生选择性裂解。结果与质子化组氨酸参与选择性切割一致。 b(+)/y(+) 的比率由残基 C 端与组氨酸的特性以及质子化组氨酸将质子转移至 C 端留下片段的能力决定。通过系统地将残基 C 末端改为组氨酸并烷基化组氨酸，进一步探讨了这一点。结果表明，b(+)/y(+) 互补离子对在双质子化 RVYIHPF 中占主导地位，而 b(5)(2+) 和 b(6)(2+) 产物离子在双质子化 RVYIHAF 光谱中占主导地位。此外，当双质子化 RVYIH*PF 中的组氨酸侧链被烷基化 (H*) 时，会观察到占主导地位的 b(5)(2+) 产物离子。基于所有结果，提出了一种涉及非典型 b 离子结构的增强组氨酸裂解的选择性断裂机制。
Enhanced gas-phase cleavage of peptides adjacent to histidine was investigated. The peptides examined were angiotensins III (RVYIHPF) and IV (VYIHPF) as well as synthetic peptide analogues with altered key residues ((R)VYI-X-Z-F; X = F or H and Z = A, P, or Sar) or a fixed charge M3P(+)CH(2)C(O)-VYIHPF. While all singly protonated peptide ions containing both histidine and arginine fragment nonselectively, the doubly protonated peptide ions with arginine and histidine, and the singly protonated peptides containing histidine but not arginine, cleave in a selective manner. In particular, dominant complementary b(+)/y(+) product ions resulting from cleavage between the HP amide bond are observed. For the fixed-charge derivative, selective cleavage occurs only if a proton is added to produce a doubly charged precursor. The results are consistent with involvement of a protonated histidine in the selective cleavage. The ratio of b(+)/y(+) is determined by the identity of the residue C-terminal to histidine and by the ability of protonated histidine to transfer a proton to the C-terminal leaving fragment. This was probed further by systematically changing the residue C-terminal to histidine and by alkylating histidine. The results indicate that while b(+)/y(+) complementary ion pairs dominate in doubly protonated RVYIHPF, b(5)(2+) and b(6)(2+) product ions dominate the spectra of doubly protonated RVYIHAF. Also, dominant b(5)(2+) product ions are observed when the histidine side chain is alkylated (H*) in doubly protonated RVYIH*PF. Based on all of the results, a selective fragmentation mechanism for enhanced cleavage at histidine involving an atypical b ion structure is proposed.