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Comparative FTIR Study of a New Fungal Rhodopsin.
MedLine Citation:
PMID:  22973982     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Bacteriorhodopsin (BR) is a light-driven proton pump of halophilic Archaea, and BR-like proton-pumping rhodopsins have been discovered in Bacteria and Eucarya as well. Leptosphaeria rhodopsin (LR) and Phaeosphaeria Rhodopsin 2 (PhaeoRD2) are both fungal rhodopsins in such a functional class, even though they belong to different branches of the phylogenetic tree. In this study, we compared light-induced structural changes in the K, L, and M photointermediates for PhaeoRD2, LR, and BR using low-temperature FTIR spectroscopy. We observed a strongly hydrogen-bonded water molecule in PhaeoRD2 (water O-D stretch in D2O at 2258 cm-1) as well as in LR and BR. This observation provided additional experimental evidence to the concept that strongly hydrogen-bonded water molecule is the functional determinant of light-driven proton pumping. The difference FTIR spectra for all the K, L, and M states are surprisingly similar between PhaeoRD2 and LR, but not for BR. PhaeoRD2 is more homologous to LR than to BR, but the difference is small. The amino acid identities between PhaeoRD2 and LR, and between PhaeoRD2 and BR are 34.5 % and 30.2 %, respectively. In addition, the amino acids uniquely identical for the fungal rhodopsins are located rather far from the retinal chromophore. In fact, the amino acid identities within 4 Å from retinal are the same among PhaeoRD2, LR, and BR. For more than 100 amino acids located within 12 Å from retinal, the identities are 48.7 % between PhaeoRD2 and LR, 46.0 % between PhaeoRD2 and BR, and 47.8 % between LR and BR. These results suggest that protein core structures are equally different among the three rhodopsins. Thus, the identical FTIR spectra between PhaeoRD2 and LR (but not BR), even for the K state, indicate that fungal rhodopsins possess some common structural motif and dynamics not obvious from the amino acid sequences.
Authors:
Hiroyasu Ito; Masayo Sumii; Akira Kawanabe; Ying Fan; Yuji Furutani; Leonid S Brown; Hideki Kandori
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-13
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  J Phys Chem B     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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