Neyroz P, Brand L, Roseman S
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
J Biol Chem. 1987 Nov 25;262(33):15900-7.
Enzyme I of the bacterial phosphoenolpyruvate: glycose phosphotransferase system has 2 tryptophan residues/monomer, as determined spectrophotometrically. The tryptophan fluorescence has been investigated with the aid of nanosecond time-resolved techniques. The decay of the fluorescence intensity was analyzed in terms of a biexponential function. The contribution of the emission associated with the shorter decay constant increases from 17-19% at 1 degree C to 43-44% at room temperature. Decay-associated spectra obtained with Enzyme I indicate different spectral distributions associated with the two decay constants. The measurement of tumbling of Enzyme I as a function of temperature revealed a transition of rotational rates between 5 and 15.5 degrees C. Global analysis allowed decomposition of the anisotropy decay into a formulation consistent with monomer and dimer rotational contributions.
通过分光光度法测定，细菌磷酸烯醇丙酮酸：葡萄糖磷酸转移酶系统的酶I每个单体含有2个色氨酸残基。已借助纳秒时间分辨技术研究了色氨酸荧光。荧光强度的衰减根据双指数函数进行分析。与较短衰减常数相关的发射贡献从1℃时的17 - 19%增加到室温时的43 - 44%。用酶I获得的衰减相关光谱表明与两个衰减常数相关的不同光谱分布。对酶I随温度变化的翻滚测量揭示了在5至15.5℃之间旋转速率的转变。全局分析允许将各向异性衰减分解为与单体和二聚体旋转贡献一致的公式。
