Structural changes of the complex between pharaonis phoborhodopsin and its cognate transducer upon formation of the m photointermediate
Structural changes of the complex between pharaonis phoborhodopsin and its cognate transducer upon formation of the m photointermediate
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DOI：
10.1021/bi047893i
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发表时间：
2005-03-01
期刊：
影响因子：
2.9
通讯作者：
Kandori, H
中科院分区：
文献类型：
--
作者：
Furutani, Y;Kamada, K;Kandori, H
法老细菌视紫红质(PPR，又称法老感觉性视紫红质II，psRII)是纳氏杆菌的负趋光性受体。它与其转导蛋白PHtrII在膜上形成2：2的复合体，在M中间体中相互作用减弱2个数量级。这种变化被认为对应于光信号向PHtrII的转移。本文将傅里叶变换红外光谱(FTIR)应用于活性M中间体在PHtrII存在和不存在的情况下。尽管有PHtrII的存在，但得到的差值FTIR光谱惊人地相似。这一结果有力地表明，PPR-pHtrII系统中的转导子激活不会引起PHtrII本身的二级结构变化。另一方面，我们发现Thr204的氢键在初级K中间体中发生了变化，但在M中间体中恢复了。Asn74在pHtrII中的氢键在M中得到加强，可能是因为与PPR的Tyr199相互作用的改变。这些事实提供了一条从受体的Lys205(视网膜)通过Thr204和Tyr199到达转导分子Asn74的光信号通路。传感器的激活可能涉及受体Thr204的松弛和传感器中Asn74的氢键变化，在此过程中，传感器的螺旋执行刚体运动，而不改变其二级结构。
pharaonis phoborhodopsin (ppR, also called pharaonis sensory rhodopsin II, psRII) is a receptor for negative phototaxis in Natronobacteritan pharaonis. It forms a 2:2 complex with its transducer protein, pHtrII, in membranes, and the association is weakened by 2 orders of magnitude in the M intermediate. Such change is believed to correspond to the transfer of the light signal to pHtrII. In this paper, we applied Fourier transform infrared (FTIR) spectroscopy to the active M intermediate in the absence and presence of pHtrII. The obtained difference FTIR spectra were surprisingly similar, notwithstanding the presence of pHtrII. This result strongly suggests that the transducer activation in the ppR-pHtrII system does not induce secondary structure alterations of the pHtrII itself. On the other hand, we found that the hydrogen bond of the OH group of Thr204 is altered in the primary K intermediate, but restored in the M intermediate. The hydrogen bond of Asn74 in pHtrII is strengthened in M, presumably because of the change in interaction with Tyr199 of ppR. These facts provided a light signaling pathway from Lys205 (retinal) of the receptor to Asn74 of the transducer through Thr204 and Tyr199. Transducer activation is likely to involve a relaxation of Thr204 in the receptor and hydrogen bonding alteration of Asn74 in the transducer, during which the helices of the transducer perform rigid-body motion without changing their secondary structures.