Document Detail

Schiff base protonation changes in Siberian hamster ultraviolet cone pigment photointermediates.
MedLine Citation:
PMID:  22394396     Owner:  NLM     Status:  MEDLINE    
Molecular structure and function studies of vertebrate ultraviolet (UV) cone visual pigments are needed to understand the molecular evolution of these photoreceptors, which uniquely contain unprotonated Schiff base linkages between the 11-cis-retinal chromophore and the opsin proteins. In this study, the Siberian hamster ultraviolet cone pigment (SHUV) was expressed and purified in an n-dodecyl-β-D-maltoside suspension for optical characterization. Time-resolved absorbance measurements, over a spectral range from 300 to 700 nm, were taken for the purified pigment at time delays from 30 ns to 4.64 s after photoexcitation using 7 ns pulses of 355 nm light. The resulting data were fit globally to a sum of exponential functions after noise reduction using singular-value decomposition. Four exponentials best fit the data with lifetimes of 1.4 μs, 210 μs, 47 ms, and 1 s. The first photointermediate species characterized here is an equilibrated mixture similar to the one formed after rhodopsin's Batho intermediate decays into equilibrium with its successor, BSI. The extremely large red shift of the SHUV Batho component relative to the pigment suggests that SHUV Batho has a protonated Schiff base and that the SHUV cone pigment itself has an unprotonated Schiff base. In contrast to SHUV Batho, the portion of the equilibrated mixture's spectrum corresponding to SHUV BSI is well fit by a model spectrum with an unprotonated Schiff base. The spectra of the next two photointermediate species revealed that they both have unprotonated Schiff bases and suggest they are analogous to rhodopsin's Lumi I and Lumi II species. After decay of SHUV Lumi II, the correspondence with rhodopsin photointermediates breaks down and the next photointermediate, presumably including the G protein-activating species, is a mixture of protonated and unprotonated Schiff base photointermediate species.
Victoria L Mooney; Istvan Szundi; James W Lewis; Elsa C Y Yan; David S Kliger
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-03-15
Journal Detail:
Title:  Biochemistry     Volume:  51     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-03-27     Completed Date:  2012-05-14     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2630-7     Citation Subset:  IM    
Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
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MeSH Terms
HEK293 Cells
Retinal Cone Photoreceptor Cells / metabolism*,  radiation effects
Retinal Pigments / chemistry*,  metabolism
Schiff Bases / chemistry*
Ultraviolet Rays*
Grant Support
EY00983/EY/NEI NIH HHS; R01 EY000983-35/EY/NEI NIH HHS; R01 EY000983-36/EY/NEI NIH HHS; R01 EY000983-37/EY/NEI NIH HHS
Reg. No./Substance:
0/Protons; 0/Retinal Pigments; 0/Schiff Bases

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