This paper is part of a Proceedings of the 12th International Conference on Retinal Proteins held at Awaji Island, Hyoyo, Japan on 4–8 June 2001.
Photoisomerization in Proteorhodopsin Mutant D97N†
Article first published online: 28 MAR 2007
Photochemistry and Photobiology
Volume 83, Issue 2, pages 226–231, March/April 2007
How to Cite
Lenz, M. O., Woerner, A. C., Glaubitz, C. and Wachtveitl, J. (2007), Photoisomerization in Proteorhodopsin Mutant D97N. Photochemistry and Photobiology, 83: 226–231. doi: 10.1562/2006-05-31-RA-909
- Issue published online: 28 MAR 2007
- Article first published online: 28 MAR 2007
- Received 31 May 2006; accepted 26 June 2006; published online 28 June 2006; DOI: 10.1562/2006-05-31-RA-909
The first steps of the photocycle of the D97N mutant of proteorhodopsin (PR) have been investigated by means of ultrafast transient absorption spectroscopy. A comparison with the primary dynamics of native PR and D85N mutant of bacteriorhodopsin is given. Upon photoexcitation of the covalently bound all-trans retinal the excited state decays biexponentially with time constants of 1.4 and 20 ps via a conical intersection, resulting in a 13-cis isomerized retinal. Neither of the two-deactivation channels is significantly preferred. The dynamics is slowed down in comparison with native PR at pH 9 and reaction rates are even lower than for native PR at pH 6, where the primary proton acceptor (Asp97) is protonated. Therefore, the ultrafast isomerization is not only controlled by the charge distribution within the retinal binding pocket. This study shows that in addition to direct electrostatics other effects have to be taken into account to explain the catalytic function of Asp97 in PR on the ultrafast isomerization reaction. This may include sterical interactions and/or bound water molecules within the retinal binding pocket.