%0 Journal Article
%A Sekharan, Sivakumar
%A Wei, Jennifer N.
%A Batista, Victor S.
%D 2012
%T The Active Site of Melanopsin: The Biological Clock
Photoreceptor
%U https://acs.figshare.com/articles/journal_contribution/The_Active_Site_of_Melanopsin_The_Biological_Clock_Photoreceptor/2463982
%R 10.1021/ja308763b.s001
%2 https://ndownloader.figshare.com/files/4106674
%K photo
%K light sensors
%K 490 nm
%K 43 nm
%K homology model
%K site mutations
%K G 89Q
%K rhod
%K 447 nm
%K Active Site
%K protonated Schiff base
%K 24 h cycles
%K circadian rhythms
%K Schiff base linkage
%K suprachiasmatic nuclei
%K crystal structure
%K melan
%K max
%K Biological Clock PhotoreceptorThe nonvisual
%K N 87Q mutation
%X The
nonvisual ocular photoreceptor melanopsin, found in the
neurons of vertebrate inner retina, absorbs blue light and triggers
the “biological clock” of mammals by activating the
suprachiasmatic nuclei (a small region of the brain that regulates
the circadian rhythms of neuronal and hormonal activities over 24
h cycles). The structure of melanopsin, however, has yet to
be established. Here, we propose for the first time a structural model
of the active site of mouse melanopsin. The homology model is
based on the crystal structure of squid rhodopsin (λmax = 490 nm) and shows a maximal absorbance (λmax = 447 nm) consistent with the observed absorption of the photoreceptor.
The 43 nm spectral shift is due to an increased bond-length alternation
of the protonated Schiff base of 11-cis-retinal chromophore,
induced by N87Q mutation and water-mediated H-bonding interactions
with the Schiff base linkage. These findings, analogous to spectral
changes observed in the G89Q bovine rhodopsin mutant, suggest
that single site mutations can convert photopigments into visual
light sensors or nonvisual sensory photoreceptors.
%I ACS Publications