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首页> 外文期刊>Biochemistry >Functionally Relevant Coupled Dynamic Profile of Bacteriorhodopsin and Lipids in Purple Membranes
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Functionally Relevant Coupled Dynamic Profile of Bacteriorhodopsin and Lipids in Purple Membranes

机译：紫质膜中细菌视紫红质和脂质的功能相关的耦合动力学概况

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The dynamics of bacteriorhodopsin (bR) and the lipid headgroups in oriented purple membranes (PMs) was determined at various temperatures and relative humidity (rh) using solid-state NMR spectroscopy.The ~(31)P NMR spectra of the alpha- and gamma-phosphate groups in methyl phosphatidylglycero-phosphate (PGP-Me),which is the major phospholipid in the PM,changed sensitively with hydration levels.Between 253 and 233 K,the signals from a fully hydrated sample became broadened similarly to those of a dry sample at 293 K.The ~(15)N cross polarization (CP) NMR spectral intensities from [~(15)N]Gly bR incorporated into fully hydrated PMs were suppressed in ~(15)N CP NMR spectra at 293 K compared with those of dry membranes but gradually recovered at low temperatures or at lower hydration (75%) levels.The suppression of the NMR signals,which is due to interference with proton decoupling frequency (approx 45 kHz),coupled with short spin-spin relaxation times (T_2) indicates that the loops of bR,in particular,have motional components around this frequency.The motion of the transmembrane alpha-helices in bR was largely affected by the freezing of excess water at low temperatures.While between 253 and 233 K,where a dynamic phase transition-like change was observed in the ~(31)P NMR spectra for the phosphate lipid headgroups,the molecular motion of the loops and the C- and N-termini slowed,suggesting lipid- loop interactions,although protein-protein interactions between stacks cannot be excluded.The results of T_2 measurements of dry samples,which do not have proton pumping activity,were similar to those for fully hydrated samples below 213 K where the M-intermediates can be trapped.These results suggest that motions in the 10s mu s correlation regime may be functionally important for the photocycle of bR,and protein-lipid interactions are motionally coupled in this dynamic regime.
机译：使用固态NMR光谱在各种温度和相对湿度（rh）下测定了细菌视紫红质（bR）和定向紫色膜（PMs）中脂质头基的动力学.α和γ的〜（31）P NMR光谱PM中的主要磷脂甲基磷脂酰甘油磷酸（PGP-Me）中的磷酸根随水合水平敏感地变化。在253和233 K之间，完全水合的样品的信号变宽，类似于干燥的样品在293 K的〜（15）N CP NMR光谱中，掺入完全水合PM中的[〜（15）N] Gly bR的〜（15）N交叉极化（CP）NMR光谱强度在293 K的〜（15）N CP NMR光谱中得到抑制。干燥膜的性能，但在低温或较低水合度（75％）时逐渐恢复.NMR信号的抑制是由于质子去耦频率（约45 kHz）受到干扰，加上自旋-自旋弛豫时间短（T_2）表示bR的环特别是在该频率附近具有运动分量。bR中跨膜α螺旋的运动很大程度上受低温下过量水的冻结影响。而在253和233 K之间，观察到了类似动态相变的变化在磷酸盐脂质头基的〜（31）P NMR光谱中，环的分子运动以及C和N末端的减慢，提示脂质-环相互作用，尽管不能排除堆叠之间的蛋白质-蛋白质相互作用。结果不具有质子泵浦活性的干燥样品的T_2测量值与213 K以下可捕获M中间体的完全水合样品的测量值相似。这些结果表明，在10s mu s相关状态下的运动可能在功能上对于bR的光循环很重要，并且蛋白质-脂质相互作用在这种动态机制中是运动耦合的。

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