Dong A, Huang P, Zhao X J, Sampath V, Caughey W S
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523.
J Biol Chem. 1994 Sep 30;269(39):23911-7.
We report here a comprehensive infrared spectroscopic study of the interactions between the anesthetic nitrous oxide (N2O) and six proteins: lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and cytochrome c oxidase. Sites occupied by N2O molecules within these proteins were characterized. Three types of hydrophobic sites were found within the proteins. One with nu 3 near 2225 cm-1 is likely to be near peptide bond carbonyls; one with nu 3 near 2219 cm-1 may be near a benzene-like structure such as the side chains of phenylalanine and tyrosine; and the other with nu 3 near 2215 cm-1 is likely to be in a nonpolar alkane-like environment provided by the side chains of Leu, Ile, and Val residues. The amount of N2O molecules bound to myoglobin increases as the pH decreases from 9.2 to 5.2. N2O-protein interactions produced no detectable changes in the ligand-binding pockets of myoglobin, hemoglobin, and cytochrome c oxidase. N2O-induced secondary structure changes were detected only in the fully reduced cytochrome c oxidase, not in the fully oxidized oxidase and the other five proteins. N2O-induced conformational changes in the alpha beta-interface of hemoglobin and the h2 and h3 alpha-helices of human serum albumin were detected by monitoring the S-H stretch vibrations of cysteine residues. These findings provide direct evidence that anesthetic N2O interacts with proteins and occupies sites in the interior of the proteins.
我们在此报告一项关于麻醉剂一氧化二氮（N₂O）与六种蛋白质相互作用的全面红外光谱研究，这六种蛋白质分别是溶菌酶、细胞色素c、肌红蛋白、血红蛋白、血清白蛋白和细胞色素c氧化酶。对这些蛋白质中N₂O分子占据的位点进行了表征。在这些蛋白质中发现了三种类型的疏水位点。一种ν₃在2225 cm⁻¹附近的位点可能靠近肽键羰基；一种ν₃在2219 cm⁻¹附近的位点可能靠近苯环结构，如苯丙氨酸和酪氨酸的侧链；另一种ν₃在2215 cm⁻¹附近的位点可能处于由亮氨酸、异亮氨酸和缬氨酸残基侧链提供的非极性烷烃样环境中。随着pH从9.2降至5.2，与肌红蛋白结合的N₂O分子数量增加。N₂O与蛋白质的相互作用在肌红蛋白、血红蛋白和细胞色素c氧化酶的配体结合口袋中未产生可检测到的变化。仅在完全还原的细胞色素c氧化酶中检测到N₂O诱导的二级结构变化，在完全氧化的氧化酶和其他五种蛋白质中未检测到。通过监测半胱氨酸残基的S - H伸缩振动，检测到N₂O诱导的血红蛋白αβ界面以及人血清白蛋白的h2和h3α螺旋的构象变化。这些发现提供了直接证据，证明麻醉剂N₂O与蛋白质相互作用并占据蛋白质内部的位点。
