Photocycle of Sensory Rhodopsin II from Halobacterium salinarum (HsSRII): Mutation of D103 Accelerates M Decay and Changes the Decay Pathway of a 13‐cis O‐like Species. (23rd April 2018)

• Record Type: Journal Article
• Authors: Dai, Gang; Geng, Xiong; Chaoluomeng, ; Tamogami, Jun; Kikukawa, Takashi; Demura, Makoto; Kamo, Naoki; Iwasa, Tatsuo
• Is Part Of: Photochemistry and photobiology. Volume 94:Number 4(2018)
• Page Start: 705
• Page End: 714
• Publication Date: 2018-04-23
• Subjects: Photochemistry -- Periodicals; Light -- Physiological effect -- Periodicals; 541.35
• DOI: 10.1111/php.12917
• Languages: English
• ISSNs: 0031-8655

Abstract

Abstract: Aspartic acid 103 (D103) of sensory rhodopsin II from Halobacterium salinarum ( Hs SRII, or also called phoborhodopsin) corresponds to D115 of bacteriorhodopsin (BR). This amino acid residue is functionally important in BR. This work reveals that a substitution of D103 with asparagine (D103N) or glutamic acid (D103E) can cause large changes in Hs SRII photocycle. These changes include (1) shortened lifetime of the M intermediate in the following order: the wild‐type > D103N > D103E; (2) altered decay pathway of a 13‐ cis O‐like species. The 13‐ cis O‐like species, tentatively named Px, was detected in Hs SRII photocycle. Px appeared to undergo branched reactions at 0°C, leading to a recovery of the unphotolyzed state and formation of a metastable intermediate, named P370, that slowly decayed to the unphotolyzed state at room temperature. In wild‐type Hs SRII at 0°C, Px mainly decayed to the unphotolyzed state, and the decay reaction toward P370 was negligible. In mutant D103E at 0°C, Px decayed to P370, while the recovery of the unphotolyzed state became unobservable. In mutant D103N, the two reactions proceeded at comparable rates. Thus, D103 of Hs SRII may play an important role in regulation of the photocycle of Hs SRII. Abstract : Substitution of D103 with asparagine (D103N) or glutamic acid (D103E) can cause large changes in Hs SRII photocycle including (1) shortened lifetime of the M intermediate in the following order: the wild‐type > D103N > D103E; (2) altered decay pathway of a 13‐ cis O‐like species (Px). In wild‐type, Px decayed via pathway 1 and/or 1′ (broken lines). In mutant D103E, Px decayed via pathway 2 (dotted line). Px of mutant D103N would decay via these pathways in comparable rates.