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BP: Fachverband Biologische Physik
BP 28: Protein structure and dynamics II
BP 28.5: Talk
Wednesday, April 2, 2014, 16:15–16:30, HÜL 386
Bistable retinal Schiff base photo-dynamics of the histidine kinase rhodopsin HKR1 from the green alga Chlamydomonas reinhardtii — •Alfons Penzkofer1, Meike Luck2, Tilo Mathes2, 3, and Peter Hegemann2 — 1Fakultät für Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany — 2Institut für Biologie/Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstrasse 42, D-10115 Berlin, Germany — 3Department of Exact Sciences / Biophysics, Vrije Universiteit, De Boolelaan 1081A, 1081 HV Amsterdam, The Netherlands
The photo-dynamics of the recombinant rhodopsin fragment of HKR1 [1] was studied. The retinal cofactor of HKR1 exists in two Schiff base forms, RetA (deprotonated 13-cis retinal) and RetB (protonated all-trans retinal). Blue light exposure converts RetB fully to RetA. UVA light exposure converts RetA to RetB and RetB to RetA giving a mixture of both. The quantum efficiencies of photo-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 occurs between RetA and RetB with a time constant of about 3 days giving mole fractions of 0.8 RetA and 0.2 RetB. Ground state and excited state potential energy curve schemes for the inter-conversion of RetA and RetB were developed. The photo-induced inter-conversions of RetA and RetB are caused by excited-state isomerization on a picosecond timescale, proton transfer, and retinal Schiff base - rhodopsin apoprotein ground-state equilibration on a millisecond timescale.
[1] M. Luck et al., J. Biol. Chem. 287 (2012) 40083.