RRC ID 31782
Author Sakai K, Imamoto Y, Su CY, Tsukamoto H, Yamashita T, Terakita A, Yau KW, Shichida Y.
Title Photochemical nature of parietopsin.
Journal Biochemistry
Abstract Parietopsin is a nonvisual green light-sensitive opsin closely related to vertebrate visual opsins and was originally identified in lizard parietal eye photoreceptor cells. To obtain insight into the functional diversity of opsins, we investigated by UV-visible absorption spectroscopy the molecular properties of parietopsin and its mutants exogenously expressed in cultured cells and compared the properties to those of vertebrate and invertebrate visual opsins. Our mutational analysis revealed that the counterion in parietopsin is the glutamic acid (Glu) in the second extracellular loop, corresponding to Glu181 in bovine rhodopsin. This arrangement is characteristic of invertebrate rather than vertebrate visual opsins. The photosensitivity and the molar extinction coefficient of parietopsin were also lower than those of vertebrate visual opsins, features likewise characteristic of invertebrate visual opsins. On the other hand, irradiation of parietopsin yielded meta-I, meta-II, and meta-III intermediates after batho and lumi intermediates, similar to vertebrate visual opsins. The pH-dependent equilibrium profile between meta-I and meta-II intermediates was, however, similar to that between acid and alkaline metarhodopsins in invertebrate visual opsins. Thus, parietopsin behaves as an "evolutionary intermediate" between invertebrate and vertebrate visual opsins.
Volume 51(9)
Pages 1933-41
Published 2012-3-6
DOI 10.1021/bi2018283
PMID 22303823
PMC PMC3315353
MeSH Animals Cone Opsins / chemistry* Eye Proteins / chemistry* Glutamic Acid / genetics Invertebrates Photochemistry Photoreceptor Cells / metabolism Phylogeny Rhodopsin / chemistry* Species Specificity Vertebrates
IF 2.865
Times Cited 7
Xenopus tropicalis Nigerian H line