Fig. 4
From: Opn5L1 is a retinal receptor that behaves as a reverse and self-regenerating photoreceptor
Detection of retinal-thio adduct formation in light-irradiated Opn5L1 by LC-MS. a Action of hydroxylamine on retinal-thio adduct in Opn5L1. In this figure, we show that C11 is the site of adduction of the retinal chromophore to C188. b Amino acid sequences of fragments containing C188 in Opn5L1NC and Opn5L1NC E177K/Q192K mutant. Structure of the expected peptide (after light irradiation in the presence of hydroxylamine, breakdown of disulfide bond between C110 and C187, carbamidomethylation of free cysteine, and tryptic digestion) is shown below. Amino acids are numbered based on the bovine rhodopsin numbering system. Numbers shown in parentheses are according to Ballesteros−Weinstein numbering. Asterisk indicates carbamidomethylation. c Mass spectrum recorded at the retention time of 12.15 min, peak time of m/z = 1045.984 ± 0.05 corresponding to isotopic m/z of [M + 2H]2+ of the peptide YGEEPYGTAC*C(retinaloxime)IDWK. The mass signals of [M + 2H]2+ and [M + 3H]3+ ions of YGEEPYGTAC*C(retinaloxime)IDWK are indicated. d, e Enlarged view of the mass signals of [M + 3H]3+ (d) and [M + 2H]2+ (e) from c, respectively. f, g LC-MS profiles of m/z = 697.659 ± 0.05 (f) and 1045.984 ± 0.05 (g) corresponding to isotopic m/z of [M + 3H]3+ and [M + 2H]2+ of the peptide YGEEPYGTAC*C(retinaloxime)IDWK, respectively. The traces obtained from the light-irradiated (red) and the dark-adapted (black) samples are shown
