Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States.
J Phys Chem B. 2022 Aug 4;126(30):5646-5654. doi: 10.1021/acs.jpcb.2c03519. Epub 2022 Jul 25.
The global motions of ubiquitin, a model protein, on the surface of anisotropically tumbling 1-palmitoyl-2-oleoyl--glycero-3-phospho-(1'-rac-glycerol) (POPG):1,2-dihexanoyl--glycero-3-phosphocholine (DHPC) bicelles are described. The shapes of POPG:DHPC bicelles prepared with high molar ratios of POPG to DHPC can be approximated by prolate ellipsoids, with the ratio of ellipsoid dimensions and dimensions themselves increasing with higher values of . Adaptation of the nuclear magnetic resonance (NMR) relaxation-based approach that we previously developed for interactions of ubiquitin with spherical POPG liposomes (Ceccon, A. 2016, 138, 5789-5792) allowed us to quantitatively analyze the variation in lifetime line broadening of NMR signals (Δ) measured for ubiquitin in the presence of = 2 POPG:DHPC bicelles and the associated transverse spin relaxation rates () of bicelle-bound ubiquitin. Ubiquitin, transiently bound to POPG:DHPC bicelles, undergoes internal rotation about an axis orthogonal to the surface of the bicelle and perpendicular to the principal axis of its rotational diffusion tensor on the low microsecond time scale (∼3 μs), while the rotation axis itself wobbles in a cone on a submicrosecond time scale (≤ 500 ns).
描述了模型蛋白泛素在各向异性翻滚的 1-棕榈酰基-2-油酰基-甘油-3-磷酸-(1'-rac-甘油)(POPG):1,2-二己酰基-甘油-3-磷酸胆碱(DHPC)双分子层表面上的全局运动。用高摩尔比的 POPG 与 DHPC 制备的 POPG:DHPC 双分子层的形状可以近似为扁长椭球体，随着的增加，椭球体尺寸的比例和尺寸本身都在增加。我们先前开发的基于核磁共振（NMR）弛豫的方法用于研究泛素与球形 POPG 脂质体的相互作用（Ceccon，A. 2016，138，5789-5792）进行了适应性调整，该方法允许我们定量分析在 = 2 POPG:DHPC 双分子层存在的情况下，测量到的泛素的 NMR 信号（Δ）的寿命线展宽变化和与之相关的双分子层结合的泛素的横向自旋弛豫率（）。在低微秒时间尺度（约 3 μs）上，瞬态结合到 POPG:DHPC 双分子层上的泛素会绕与其旋转扩散张量的主轴垂直且垂直于双分子层表面的轴进行内部旋转，而旋转轴本身会在亚微秒时间尺度（≤500 ns）内以圆锥形式摆动。
