Takao K, Kikukawa T, Araiso T, Kamo N
Laboratory of Biophysical Chemistry, Faculty of Pharmaceutical Sciences, Sapporo, 060-0812 Japan.
Biophys Chem. 1998 Jul 13;73(1-2):145-53. doi: 10.1016/s0301-4622(98)00156-2.
Natronobacterium pharaonis has retinal proteins, one of which is pharaonis phoborhodopsin, abbreviated as ppR (or called pharaonis sensory rhodopsin II, psR-II). This pigment protein functions as a photoreceptor of the negative phototaxis of this bacterium. On photoexcitation ppR undergoes photocycling; the photoexcited state relaxes in the dark and returns to the original state via several intermediates. The photocycle of ppR resembles that of bR except in wavelengths and rate. The cycle of bR is completed in 10 ms while that of ppR takes seconds. The Arrhenius analysis of M-intermediate (ppR(M)) decay which is rate-limiting revealed that the slow decay is due to the large negative activation entropy of ppR. The addition of azide increases the decay rate 300-fold (at pH 7); Arrhenius analysis revealed decreases in the activation energy (activation enthalpy) and a further decrease in the activation entropy.
法老盐杆菌含有视黄醛蛋白，其中一种是法老视紫红质，简称为ppR（或称为法老感官视紫红质II，psR-II）。这种色素蛋白作为该细菌负趋光性的光感受器发挥作用。在光激发下，ppR会经历光循环；光激发态在黑暗中弛豫，并通过几种中间体回到原始状态。ppR的光循环与细菌视紫红质（bR）的光循环相似，只是在波长和速率方面有所不同。bR的循环在10毫秒内完成，而ppR的循环需要数秒。对限速的M中间体（ppR(M)）衰变进行的阿仑尼乌斯分析表明，缓慢衰变是由于ppR具有很大的负活化熵。叠氮化物的加入使衰变速率提高了300倍（在pH 7时）；阿仑尼乌斯分析表明活化能（活化焓）降低，活化熵进一步降低。
