Tetramer formation kinetics in the signaling state of AppA monitored by time-resolved diffusion
Tetramer formation kinetics in the signaling state of AppA monitored by time-resolved diffusion
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DOI：
10.1529/biophysj.106.083915
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发表时间：
2006-07-15
影响因子：
3.4
通讯作者：
Terazima, Masahide
中科院分区：
文献类型：
--
作者：
Hazra, Partha;Inoue, Keiichi;Terazima, Masahide
用脉冲激光诱导的瞬时光栅法研究了APPA(5-125)的BLUF结构域光反应动力学。研究发现，光生产物的D与时间有关。从反应速率的浓度依赖关系可以得出结论，APPA的BLUF结构域在光激发下形成二聚体。由于APPA在基态以二聚体形式存在，这种二聚化反应表明四聚体的形成处于信号态。从观察到的速率常数(k(Obs))对APPA浓度的斜率，确定二级速率常数与2.5×10~(-5)M~(-1)S(~(-1))相似，比扩散控制反应低4个数量级。这表明蛋白质分子在二聚化过程中的相对取向会造成额外的限制，从而减缓反应速度。
The photoreaction kinetics of the BLUF domain of AppA(5-125) was studied by monitoring time-dependence of an apparent diffusion coefficient (D) using the pulsed laser-induced transient grating technique. It was found that D of the photoproduct is time-dependent. From the concentration dependence of the reaction rate, it was concluded that the BLUF domain of AppA forms a dimer upon the photoexcitation. Since AppA exists as a dimeric form in the ground state, this dimerization reaction indicates the tetramer formation in the signaling state. From the slope of the plot of observed rate constants (k(obs)) against the AppA concentration, the second order rate constant is determined to be similar to 2.5 x 10(5) M-1 s(-1), which is similar to 4 orders in magnitude lower than the diffusion controlled reaction. It indicates that a relative orientation of the protein molecules during the dimerization process causes additional constraints, which slow down the reaction rate.