title: Modulation of thermal noise and spectral sensitivity in Lake Baikal cottoid fish rhodopsins.
abstract: Lake Baikal is the deepest and one of the most ancient lakes in the world. Its unique ecology has resulted in the colonization of a diversity of depth habitats by a unique fauna that includes a group of teleost fish of the sub-order Cottoidei. This relatively recent radiation of cottoid fishes shows a gradual blue-shift in the wavelength of the absorption maximum of their visual pigments with increasing habitat depth. Here we combine homology modeling and quantum chemical calculations with experimental in vitro measurements of rhodopsins to investigate dim-light adaptation. The calculations, which were able to reproduce the trend of observed absorption maxima in both A1 and A2 rhodopsins, reveal a Barlow-type relationship between the absorption maxima and the thermal isomerization rate suggesting a link between the observed blue-shift and a thermal noise decrease. A Nakanishi point-charge analysis of the electrostatic effects of non-conserved and conserved amino acid residues surrounding the rhodopsin chromophore identified both close and distant sites affecting simultaneously spectral tuning and visual sensitivity. We propose that natural variation at these sites modulate both the thermal noise and spectral shifting in Baikal cottoid visual pigments resulting in adaptations that enable vision in deep water light environments.
authors.affiliation: Chemistry Department, Bowling Green State University, Bowling Green OH 43403, USA.
authors.forename: Hoi Ling
authors.initials: HL
authors.lastname: Luk
authors.affiliation: Department of Ecology and Evolutionary Biology and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, ON M5S 3G5, Canada.
authors.forename: Nihar
authors.initials: N
authors.lastname: Bhattacharyya
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Siena, I-53100, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Montisci
authors.affiliation: Department of Ecology and Evolutionary Biology and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, ON M5S 3G5, Canada.
authors.forename: James M
authors.initials: JM
authors.lastname: Morrow
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Siena, I-53100, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Melaccio
authors.affiliation: Department of Organic Chemistry for Life Science, Kobe Pharmaceutical University, 4-19-1 Motoyamakita-machi, Higashinada-ku, Kobe 658-8558, Japan.
authors.forename: Akimori
authors.initials: A
authors.lastname: Wada
authors.affiliation: Department of Organic Chemistry, Weizman Institute of Science, 234 Herzl Street, Rehovot 7610001, Israel.
authors.forename: Mudi
authors.initials: M
authors.lastname: Sheves
authors.affiliation: Department of Life Sciences, University of Modena and Reggio Emilia, I-41125 Modena, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Fanelli
authors.affiliation: Department of Ecology and Evolutionary Biology and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, ON M5S 3G5, Canada.
authors.forename: Belinda S W
authors.initials: BS
authors.lastname: Chang
authors.affiliation: Chemistry Department, Bowling Green State University, Bowling Green OH 43403, USA.|Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Siena, I-53100, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D000596:Amino Acids; D000818:Animals; D005399:Fishes; D060106:Lakes; D008027:Light; D008958:Models, Molecular; D008968:Molecular Conformation; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D012243:Rhodopsin