プロテイン・バックボーン 1H(N) -13 カルファおよび15N-13 カルファ残留二極およびJ結合:NMR構造決定のための新しい制約
Keyang Ding1, Angela M Gronenborn
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Journal of the American Chemical Society
|May 20, 2004
まとめ
この研究では,タンパク質の骨幹結合を測定するための敏感な方法が導入され,正確な構造の決定を可能にします. この技術は,二面角や二次構造のような結合とタンパク質の構造的特徴の関係を確立します.
科学分野:
- バイオケミストリー バイオケミストリー
- 構造生物学 構造生物学とは
- 核磁共振 (NMR) スペクトロスコピー
背景:
- タンパク質の核スピン結合の正確な測定は,タンパク質の3次元構造の決定に不可欠です.
- 既存の方法は,日常的な分析に必要な感度や簡素さが欠けている可能性があります.
研究 の 目的:
- タンパク質の骨幹窒素-炭素 (15N-13Calpha) と窒素-水素-炭素 (1HN-13Calpha) の結合を測定するための,単純で感度が向上した実験的アプローチを開発する.
- 測定された結合を,既知のタンパク質構造と比較することによって,その方法を検証する.
- 構造情報を導き出すためのこれらの結合の有用性を探求する.
主な方法:
- 新しい,感度強化されたNMR実験が設計され,実装されました.
- 残留二極結合 (2DHCA, 1DNCA, 3DHCA, 2DNCA) は,タンパク質 GB1.1 に対して測定されました.
- 実験データは,GB1の確立されたNMR構造 (PDBコード:3GB1) と比較した.
主要な成果:
- この実験では,バックボーン15N-13Calphaと1HN-13Calphaの結合を正確に測定することができました.
- 測定された残留二極結合は,タンパク質GB1. 1の精製されたNMR構造と優れた一致を示した.
- 単一結合の1JNCAカップリングとバックボーン二面サイコーンの間のKarplusタイプの関係が確認されました.
- 二重結合2JNCAカップリングは,二次構造インデックスの確立に有効であることが示されました.
結論:
- 開発された方法は,タンパク質の脊髄結合の正確な測定のためのシンプルで敏感なツールです.
- これらのカップリングは,高解像度のNMR構造決定と二次構造分析に価値があります.
- この発見は,タンパク質構造の解明のためのNMR技術の進歩に寄与する.
さらに関連する動画
関連する概念動画
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
Carbon-13 (¹³C) NMR: Overview
Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...


