Single-conformation spectroscopy of cold, protonated D PG-containing peptides: switching β-turn types and formation of a sequential type II/II′ double β-turn
Single-conformation spectroscopy of cold, protonated D PG-containing peptides: switching β-turn types and formation of a sequential type II/II′ double β-turn
复制标题
含冷质子化 D PG 肽的单构象光谱：切换 β 转角类型并形成连续的 II/II 型双 β 转角
DOI：
10.1039/d1cp04852j
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发表时间：
2022
影响因子：
3.3
通讯作者：
Zwier, Timothy S.
中科院分区：
文献类型：
--
作者：
Lawler, John T.;Harrilal, Christopher P.;DeBlase, Andrew F.;Sibert, Edwin L.;McLuckey, Scott A.;Zwier, Timothy S.
D-脯氨酸（DPro，DP）被广泛用于在工程化肽中形成β-发夹环，否则这些肽将是非结构化的，最常见的是作为形成β-转角的DPG亚基的一部分。为了观察DPG是否在短质子化肽中促进了这种效应，在氢化物拉伸（2800-3700 cm-1）和酰胺I/II（1400-1800 cm-1）区域中进行了五肽YAPGA的冷（~ 10 K）质子化DP和LP非对映体的构象特异性IR-UV双共振光碎片光谱。为了更好地描述通常与酰胺I振动相关的1600-1800 cm−1区域，开发了一个模型局域化哈密顿量。在这些质子化肽中，CO拉伸基本原理与NH3+基团的N-H弯曲基本原理经历了广泛的混合。该模型的哈密顿量占实验定量的细节。在DP非对映异构体中，所有的群体被汇集成单个构象异构体，其呈现为II型β-转角，其中A和DP分别在i + 1和i + 2位置。这种结构不是我们根据溶液相倾向假设的预期的II型β-转向。构象能谱分析表明，空间和电荷诱导效应在II型β-转角的优先形成中起作用。相比之下，LP异构体形成三种结构非常不同的构象，其中没有一种是II/II′ β-转角，证实LPG不是β-转角形成剂。最后，还对延伸肽[YAADPGAAA + H]+进行了单构象光谱，以确定质子化N末端进一步远离DPG是否会导致β-发夹形成。尽管将其整个群体汇集到单个肽骨架结构中，但指定的结构不是β-发夹，而是串联的II型/II '型双β-转角，其将肽骨架横向位移约7.5 Å，但保留骨架定向在其原始方向上。
D-Proline (DPro, DP) is widely utilized to form β-hairpin loops in engineered peptides that would otherwise be unstructured, most often as part of a DPG sub-unit that forms a β-turn. To observe whether DPG facilitated this effect in short protonated peptides, conformation specific IR–UV double resonance photofragment spectra of the cold (∼10 K) protonated DP and LP diastereomers of the pentapeptide YAPGA was carried out in the hydride stretch (2800–3700 cm−1) and amide I/II (1400–1800 cm−1) regions. A model localized Hamiltonian was developed to better describe the 1600–1800 cm−1 region commonly associated with the amide I vibrations. The CO stretch fundamentals experience extensive mixing with the N–H bending fundamentals of the NH3+ group in these protonated peptides. The model Hamiltonian accounts for experiment in quantitative detail. In the DP diastereomer, all the population is funneled into a single conformer which presented as a type II β-turn with A and DP in the i + 1 and i + 2 positions, respectively. This structure was not the anticipated type II′ β-turn across DPG that we had hypothesized based on solution-phase propensities. Analysis of the conformational energy landscape shows that both steric and charge-induced effects play a role in the preferred formation of the type II β-turn. In contrast, the LP isomer forms three conformations with very different structures, none of which were type II/II′ β-turns, confirming that LPG is not a β-turn former. Finally, single-conformation spectroscopy was also carried out on the extended peptide [YAADPGAAA + H]+ to determine whether moving the protonated N-terminus further from DPG would lead to β-hairpin formation. Despite funneling its entire population into a single peptide backbone structure, the assigned structure is not a β-hairpin, but a concatenated type II/type II′ double β-turn that displaces the peptide backbone laterally by about 7.5 Å, but leaves the backbone oriented in its original direction.