Functionally relevant coupled dynamic profile of bacteriorhodopsin and lipids in purple membranes
Functionally relevant coupled dynamic profile of bacteriorhodopsin and lipids in purple membranes
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DOI：
10.1021/bi051756j
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发表时间：
2006-04-04
期刊：
影响因子：
2.9
通讯作者：
Watts, A
中科院分区：
文献类型：
--
作者：
Kamihira, M;Watts, A
在不同温度和相对湿度（RH）下，使用固态NMR光谱法测定了定向紫膜（PMs）中细菌视紫红质（bR）和脂质头基的动力学。甲基磷脂酰甘油磷酸盐（PGP-Me）中的α-和γ-磷酸基团的P-31 NMR光谱（PGP-Me是PM中的主要磷脂）随水合水平敏感地变化。在253和233 K之间，来自完全水合的样品的信号变得与293 K下的干燥样品的信号类似地变宽。N-15交叉极化（CP）NMR光谱强度从[N-15]Gly bR纳入到完全水合的PM在N-15 CP NMR光谱在293 K相比，干膜，但逐渐恢复在低温下或在较低的水化（75%）的水平。NMR信号的抑制，这是由于质子去耦频率（类似于45 kHz）的干扰，加上短自旋-自旋弛豫时间（T-2）表明，bR的环，特别是具有运动的组件在这个频率。bR中的跨膜α-螺旋的运动在很大程度上受低温下过量水的冻结的影响。而在253和233 K之间，在P-31 NMR谱中观察到磷酸脂头基的动态相变样变化，环和C-和N-末端的分子运动减慢，表明脂质-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。干燥样品的T-2测量的结果，不具有质子泵活性，是类似于那些完全水合的样品低于213 K的M-中间体可以被捕获。这些结果表明，在10 μ s的相关制度的议案可能是功能上重要的光周期的bR，和蛋白质-脂质相互作用的运动耦合在这个动态的制度。
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 P-31 NMR spectra of the alpha- and gamma-phosphate groups in methyl phosphatidylglycerophosphate (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 N-15 cross polarization (CP) NMR spectral intensities from [N-15]Gly bR incorporated into fully hydrated PMs were suppressed in N-15 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 (similar to 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 P-31 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.