Role of the polarity of the heme environment for the CO stretch modes in cytochrome P-450cam-CO.
Role of the polarity of the heme environment for the CO stretch modes in cytochrome P-450cam-CO.
复制标题
血红素环境极性对细胞色素 P-450cam-CO 中 CO 拉伸模式的作用。
作者：
C. Jung;H. Schulze;E. Deprez
使用 FT 红外光谱测量细胞色素 P-450cam-CO 各种底物复合物的 CO 拉伸模式。在室温下，大多数配合物显示出单一但通常不对称的红外波段。当氧化蛋白质中的底物诱导的高自旋含量减少时，各种复合物的该带的代表性波数增加。此外，CO伸缩波数的增加（1939至1956 cm-1）与Soret带波数的减少（22440至22373 cm-1）相关。有人认为，由于血红素环境对水分子的可及性发生了变化，血红素袋的极性受到底物的调节。增加的水含量补偿了CO配体附近的正静电势，这导致CO与I螺旋的接触松动。
The CO stretch mode of various substrate complexes of cytochrome P-450cam-CO was measured using FT infrared spectroscopy. At room temperature most of the complexes show a single, but often asymmetric infrared band. The representative wavenumber of this band for the various complexes increases when the high-spin content, induced by the substrates in the oxidized protein, decreases. Additionally, the increase of the CO stretch wavenumber (1939 to 1956 cm-1) correlates with the decrease of the Soret band wavenumber (22440 to 22373 cm-1). It is suggested that the polarity of the heme pocket is modulated by the substrates due to changed accessibility of the heme environment for water molecules. The increased water content compensates positive electrostatic potentials near the CO ligand, which results in loosening the contact of CO to the I helix.