Structural Changes of the Complex between pharaonis Phoborhodopsin and Its Cognate Transducer upon Formation of the M Photointermediate

详细信息    查看全文

• 作者：Yuji Furutani ; Kentaro Kamada ; Yuki Sudo ; Kazumi Shimono ; Naoki Kamo ; and Hideki Kandori
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：March 1, 2005
• 年：2005
• 卷：44
• 期：8
• 页码：2909 - 2915
• 全文大小：305K
• 年卷期：v.44,no.8(March 1, 2005)
• ISSN：1520-4995

文摘

pharaonis phoborhodopsin (ppR, also called pharaonis sensory rhodopsin II, psRII) is a receptorfor negative phototaxis in Natronobacterium 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, weapplied Fourier transform infrared (FTIR) spectroscopy to the active M intermediate in the absence andpresence of pHtrII. The obtained difference FTIR spectra were surprisingly similar, notwithstanding thepresence of pHtrII. This result strongly suggests that the transducer activation in the ppR-pHtrII systemdoes not induce secondary structure alterations of the pHtrII itself. On the other hand, we found that thehydrogen bond of the OH group of Thr204 is altered in the primary K intermediate, but restored in theM intermediate. The hydrogen bond of Asn74 in pHtrII is strengthened in M, presumably because of thechange 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 islikely to involve a relaxation of Thr204 in the receptor and hydrogen bonding alteration of Asn74 in thetransducer, during which the helices of the transducer perform rigid-body motion without changing theirsecondary structures.