Devanathan S, Lin S, Cusanovich M A, Woodbury N, Tollin G
Department of Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
Biophys J. 2000 Oct;79(4):2132-7. doi: 10.1016/S0006-3495(00)76460-5.
Transient absorption spectroscopy in the time range from -1 ps to 4 ns, and over the wavelength range from 420 to 550 nm, was applied to the Glu46Gln mutant of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila. This has allowed us to elucidate the kinetic constants of excited state formation and decay and photochemical product formation, and the spectral characteristics of stimulated emission and the early photocycle intermediates. Both the quantum efficiency ( approximately 0.5) and the rate constants for excited state decay and the formation of the initial photochemical intermediate (I(0)) were found to be quite similar to those obtained for wild-type PYP. In contrast, the rate constants for the formation of the subsequent photocycle intermediates (I(0)(double dagger) and I(1)), as well as for I(2) and for ground state regeneration as determined in earlier studies, were found to be from 3- to 30-fold larger. The structural implications of these results are discussed.
我们对嗜盐外硫红螺菌光活性黄色蛋白（PYP）的Glu46Gln突变体进行了瞬态吸收光谱研究，时间范围为-1皮秒至4纳秒，波长范围为420至550纳米。这使我们能够阐明激发态形成与衰减以及光化学产物形成的动力学常数，以及受激发射和早期光循环中间体的光谱特征。结果发现，量子效率（约0.5）以及激发态衰减和初始光化学中间体（I(0)）形成的速率常数与野生型PYP的非常相似。相比之下，后续光循环中间体（I(0)‡和I(1)）形成的速率常数，以及早期研究中确定的I(2)和基态再生的速率常数要大3至30倍。本文讨论了这些结果的结构意义。
