Conformation-Specific Spectroscopy of Asparagine-Containing Peptides: Influence of Single and Adjacent Asn Residues on Inherent Conformational Preferences
Conformation-Specific Spectroscopy of Asparagine-Containing Peptides: Influence of Single and Adjacent Asn Residues on Inherent Conformational Preferences
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DOI：
10.1021/acs.jpca.8b08418
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发表时间：
2018-11-08
影响因子：
2.9
通讯作者：
Zwier, Timothy S.
中科院分区：
文献类型：
--
作者：
Blodgett, Karl N.;Fischer, Joshua L.;Zwier, Timothy S.
在气相喷冷条件下，记录了Ac-Asn-NHBn、Ac-Ala-Asn-NHBn和Ac-Asn-Asn-NHBn等一系列封端天冬酰胺多肽的红外光谱和紫外光谱，以探讨ASN残基及其-CH2-C(=O)-NH2侧链对肽骨架局部构象偏好的影响。利用共振离子浸渍红外光谱(RIDIR)和红外-紫外烧孔光谱(IR-UV HB)的双共振法分别在红外和紫外区记录单一构象光谱，不受分子束中存在的其他构象的干扰。AC-ASN-NHBn的种群分布在两种构象上，这两种构象都形成了天冬氨酸氨基与多肽骨架上的NH和C=O基团之间的桥梁。在一种中，肽主链与7元H键环(标记为C-eq(7))相结合，从而形成由C6/C7ASN桥稳定的逆伽马转折。在另一种情况下，天冬氨酸氨基形成C8/C7H键桥，而羧胺基团在涉及CS相互作用的延伸的肽骨架上朝向相反的方向。Ac-Ala-Asn-NHBn和Ac-Asn-Asn-NHBn都只以单一构象存在，其中肽骨架与其C10氢键进行I型β转折。天冬氨酸残基(S)通过羧胺C=O基团与相同残基的酰胺NH之间的C6H键(S)稳定这一β转折。这些结构与先前研究的含有Gin的多肽中的相应结构非常相似[Walsh，P.S.等人。PCCP2016，18,11306-11322；沃尔什，P.S.等人。安吉。化学。内部艾德2016，55,14618-14622]，表明Asn和Gln侧链可以各自配置以稳定相同的主干构象。光谱和计算证据表明，谷氨酰胺比天冬酰胺更容易通过异常强烈的侧链主干氢键形成β转角。进一步介绍和讨论了由于这些相似氨基酸的侧链长度不同而导致的光谱和结构的相似性和差异性。
The infrared and ultraviolet spectra of a series of capped asparagine-containing peptides, Ac-Asn-NHBn, Ac-Ala-Asn-NHBn, and Ac-Asn-Asn-NHBn, have been recorded under jet-cooled conditions in the gas phase in order to probe the influence of the Asn residue, with its -CH2-C(= O)-NH2 side chain, on the local conformational preferences of a peptide backbone. The double-resonance methods of resonant ion-dip infrared (RIDIR) spectroscopy and infrared-ultraviolet hole burning (IR-UV HB) spectroscopy were used to record single conformation spectra in the infrared and ultraviolet, respectively, free from interference from other conformations present in the molecular beam. Ac-Asn-NHBn spreads its population over two conformations, both of which bonds that form a bridge between the Asn carboxamide group and the NH and C = O groups on the peptide backbone. In one the peptide backbone engages in a 7-membered H-bonded ring (labeled C-eq(7)), thereby forming an inverse gamma-turn, stabilized by a C6/C7 Asn bridge. In the other the Asn carboxamide group forms a C8/C7 H-bonded bridge with the carboxamide group facing in the opposite direction across an extended peptide backbone involving a CS interaction. Both Ac-Ala-Asn-NHBn and Ac-Asn-Asn-NHBn are found exclusively in a single conformation in which the peptide backbone engages in a type I beta-turn with its C10 H-bond. The Asn residue(s) stabilize this beta-turn via C6 H-bond(s) between the carboxamide C = O group and the same residue's amide NH. These structures are closely analogous to the corresponding structures in Gin-containing peptides studied previously [Walsh, P. S. et al. PCCP 2016, 18, 11306-11322; Walsh, P. S. et al. Angew. Chem. Int. Ed. 2016, 55, 14618-14622], indicating that the Asn and Gln side chains can each configure so as to stabilize the same backbone conformations. Spectroscopic and computational evidence suggest that glutamine is more predisposed than asparagine to beta-turn formation via unusually strong side-chain-backbone hydrogen-bond formation. Further spectral and structural similarities and differences due to the side-chain length difference of these similar amino acids are presented and discussed.