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Functional importance of the oligomer formation of the cyanobacterial H+ pump Gloeobacter rhodopsin

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Title: Functional importance of the oligomer formation of the cyanobacterial H+ pump Gloeobacter rhodopsin
Authors: Iizuka, Azusa Browse this author
Kajimoto, Kousuke Browse this author
Fujisawa, Tomotsumi Browse this author →KAKEN DB
Tsukamoto, Takashi Browse this author →KAKEN DB
Aizawa, Tomoyasu Browse this author →KAKEN DB
Kamo, Naoki Browse this author
Jung, Kwang-Hwan Browse this author
Unno, Masashi Browse this author →KAKEN DB
Demura, Makoto Browse this author →KAKEN DB
Kikukawa, Takashi Browse this author →KAKEN DB
Issue Date: 24-Jul-2019
Publisher: Nature Publishing Group
Journal Title: Scientific reports
Volume: 9
Start Page: 10711
Publisher DOI: 10.1038/s41598-019-47178-5
PMID: 31341208
Abstract: Many microbial rhodopsins self-oligomerize, but the functional consequences of oligomerization have not been well clarified. We examined the effects of oligomerization of a H+ pump, Gloeobacter rhodopsin (GR), by using nanodisc containing trimeric and monomeric GR. The monomerization did not appear to affect the unphotolyzed GR. However, we found a significant impact on the photoreaction: The monomeric GR showed faint M intermediate formation and negligible H+ transfer reactions. These changes reflected the elevated pKa of the Asp121 residue, whose deprotonation is a prerequisite for the functional photoreaction. Here, we focused on His87, which is a neighboring residue of Asp121 and conserved among eubacterial H+ pumps but replaced by Met in an archaeal H+ pump. We found that the H87M mutation removes the "monomerization effects": Even in the monomeric state, H87M contained the deprotonated Asp121 and showed both M formation and distinct H+ transfer reactions. Thus, for wild-type GR, monomerization probably strengthens the Asp121-His87 interaction and thereby elevates the pKa of Asp121 residue. This strong interaction might occur due to the loosened protein structure and/or the disruption of the interprotomer interaction of His87. Thus, the trimeric assembly of GR enables light-induced H+ transfer reactions through adjusting the positions of key residues.
Type: article
Appears in Collections:生命科学院・先端生命科学研究院 (Graduate School of Life Science / Faculty of Advanced Life Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
国際連携研究教育局 : GI-CoRE (Global Institution for Collaborative Research and Education : GI-CoRE) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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