Bistable Retinal Schiff Base Photodynamics of Histidine Kinase Rhodopsin HKR1 from Chlamydomonas reinhardtii. (8th March 2014)

• Record Type: Journal Article
• Authors: Penzkofer, Alfons; Luck, Meike; Mathes, Tilo; Hegemann, Peter
• Is Part Of: Photochemistry and photobiology. Volume 90:Number 4(2014:Jul./Aug.)
• Page Start: 773
• Page End: 785
• Publication Date: 2014-03-08
• Subjects: Photochemistry -- Periodicals; Light -- Physiological effect -- Periodicals; 541.35
• DOI: 10.1111/php.12246
• Languages: English
• ISSNs: 0031-8655

Abstract

<abstract abstract-type="main" id="php12246-abs-0001"> <title>Abstract</title> <p>The photodynamics of the recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from <italic>Chlamydomonas reinhardtii</italic> was studied by absorption and fluorescence spectroscopy. The retinal cofactor of HKR1 exists in two Schiff base forms RetA and RetB. RetA is the deprotonated 13‐<italic>cis</italic>‐retinal Schiff base (RSB) absorbing in the UVA spectral region. RetB is the protonated all‐<italic>trans</italic> 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.</p> </abstract>