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Bistable Retinal Schiff Base Photodynamics of Histidine Kinase Rhodopsin HKR 1 from Chlamydomonas reinhardtii
Author(s) -
Penzkofer Alfons,
Luck Meike,
Mathes Tilo,
Hegemann Peter
Publication year - 2014
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12246
Subject(s) - physics , photochemistry , chlamydomonas reinhardtii , fluorescence , stereochemistry , biology , chemistry , biochemistry , gene , mutant , quantum mechanics
The photodynamics of the recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR 1 from Chlamydomonas reinhardtii was studied by absorption and fluorescence spectroscopy. The retinal cofactor of HKR 1 exists in two Schiff base forms RetA and RetB. RetA is the deprotonated 13‐ cis ‐retinal Schiff base (RSB) absorbing in the UVA spectral region. RetB is the protonated all‐ trans RSB absorbing in the blue spectral region. Blue light exposure converts RetB fully to RetA. UVA light exposure converts RetA to RetB and RetB to RetA giving a mixture determined by their absorption cross sections and their conversion efficiencies. The quantum efficiencies of conversion of RetA to RetB and RetB to RetA were determined to be 0.096 ± 0.005 and 0.405 ± 0.01 respectively. In the dark thermal equilibration between RetA and RetB with dominant RetA content occurred with a time constant of about 3 days at room temperature. The fluorescence emission behavior of RetA and RetB was studied, and fluorescence quantum yields of ϕ F (RetA) = 0.00117 and ϕ F (RetB) = 9.4 × 10 −5 were determined. Reaction coordinate schemes of the photodynamics are developed.