title: Modulation of the absorption maximum of rhodopsin by amino acids in the C-terminus.
abstract: Vision begins when light is absorbed by visual pigments. It is commonly believed that the absorption spectra of visual pigments are modulated by interactions between the retinal and amino acids within or near 4.5 angstroms of the retinal in the transmembrane (TM) segments. However, this dogma has not been rigorously tested. In this study, we show that the retinal-opsin interactions extend well beyond the retinal binding pocket. We found that, although it is positioned outside of TM segments, the C-terminus of the rhodopsin in the rockfish longspine thornyhead (Sebastolobus altivelis) modulates its lambda(max) by interacting mainly with the last TM segment. Our results illustrate how amino acids in the C-terminus are likely to interact with the retinal. We anticipate our analyses to be a starting point for viewing the spectral tuning of visual pigments as interactions between the retinal and key amino acids that are distributed throughout the entire pigment.
authors.affiliation: Department of Biology, Emory University, Atlanta, GA, USA. syokoya@emory.edu
authors.forename: Shozo
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Tada
authors.forename: Takahisa
authors.initials: T
authors.lastname: Yamato
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D017931:DNA Primers / Q000235:genetics; D005399:Fishes / Q000235:genetics; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010777:Photochemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012243:Rhodopsin / Q000737:chemistry* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013053:Spectrophotometry
chemical_list: D000596:Amino Acids; D017931:DNA Primers; D011994:Recombinant Proteins; D012243:Rhodopsin