Butko P, He J, Nicholls P
Department of Biological Sciences, Brock University, St. Catharines, Ont., Canada.
Biochem Biophys Res Commun. 1992 Dec 30;189(3):1477-83. doi: 10.1016/0006-291x(92)90241-c.
The spectrum of resting cytochrome c oxidase is modulated by valinomycin addition, which induces a red shift of the Soret band. The enzyme is known both to fluoresce and phosphorescence, effects which can be modulated by certain protein reagents and quenchers. Valinomycin had little effect upon fluorescence at 335 nm, whether excited at 295 nm or 280 nm (tryptophans or both tryptophans and tyrosines, respectively). Phosphorescence at 445 nm was slightly enhanced upon the binding of valinomycin to the enzyme, suggesting a small conformational change accompanying the spectral shift of the heme groups. The quenching by nitrite of the phosphorescence excited at 260 nm, but not that excited at 295 nm, was diminished by valinomycin. This suggests that the valinomycin-induced conformational change may involve (i) a change in the accessibility of tyrosines to the quencher and/or (ii) a change in distribution of distances and/or orientations between populations of tyrosines and tryptophans.
添加缬氨霉素可调节静息细胞色素c氧化酶的光谱，这会导致索雷特带发生红移。已知该酶会发出荧光和磷光，某些蛋白质试剂和猝灭剂可调节这些效应。无论在295nm（分别为色氨酸或色氨酸和酪氨酸）还是280nm激发，缬氨霉素对335nm处的荧光几乎没有影响。缬氨霉素与该酶结合后，445nm处的磷光略有增强，这表明伴随着血红素基团的光谱位移会发生微小的构象变化。缬氨霉素可减少亚硝酸盐对260nm激发的磷光的猝灭作用，但对295nm激发的磷光猝灭作用无影响。这表明缬氨霉素诱导的构象变化可能涉及：（i）酪氨酸与猝灭剂可及性的变化和/或（ii）酪氨酸和色氨酸群体之间距离和/或取向分布的变化。
