Galkin O, Buchter S, Tabirian A, Schulte A
Department of Physics and Center for Research and Education in Optics and Lasers, University of Central Florida, Orlando 32816-2385, USA.
Biophys J. 1997 Nov;73(5):2752-63. doi: 10.1016/S0006-3495(97)78304-8.
The influence of high pressure on the heme protein conformation of myoglobin in different ligation states is studied using Raman spectroscopy over the temperature range from 30 to 295 K. Photostationary experiments monitoring the oxidation state marker bands demonstrate the change of rebinding rate with pressure. While frequency changes of vibrational modes associated with rigid bonds of the porphyrin ring are <1 cm(-1), we investigate a significant shift of the iron-histidine mode to higher frequency with increasing pressure (approximately 3 cm(-1) for deltaP = 190 MPa in Mb). The observed frequency shift is interpreted structurally as a conformational change affecting the tilt angle between the heme plane and the proximal histidine and the out-of-plane iron position. Independent evidence for iron motion comes from measurements of the redshift of band III in the near-infrared with pressure. This suggests that at high pressure the proximal heme pocket and the protein are altered toward the bound state conformation, which contributes to the rate increase for CO binding. Raman spectra of Mb and photodissociated MbCO measured at low temperature and variable pressure further support changes in protein conformation and are consistent with glasslike properties of myoglobin below 160 K.
利用拉曼光谱在30至295 K的温度范围内研究了高压对处于不同连接状态的肌红蛋白血红素蛋白构象的影响。监测氧化态标记带的光稳态实验表明了再结合速率随压力的变化。虽然与卟啉环刚性键相关的振动模式的频率变化<1 cm⁻¹，但我们研究发现随着压力增加，铁-组氨酸模式向更高频率有显著位移（在肌红蛋白中，对于ΔP = 190 MPa，约为3 cm⁻¹）。观察到的频率位移在结构上被解释为一种构象变化，它影响血红素平面与近端组氨酸之间的倾斜角以及平面外铁的位置。铁运动的独立证据来自于带III在近红外区域随压力的红移测量。这表明在高压下，近端血红素口袋和蛋白质向结合态构象改变，这有助于增加CO结合的速率。在低温和可变压力下测量的肌红蛋白和光解离的肌红蛋白一氧化碳复合物的拉曼光谱进一步支持了蛋白质构象的变化，并且与低于160 K时肌红蛋白的玻璃状性质一致。
