Web Release Date: March 20,
The LOV2 Domain of Phototropin: A Reversible Photochromic Switch
and
Department of Biophysics, Faculty of Sciences, Vrije Universiteit, 1081HV Amsterdam, The Netherlands, and Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois
Received December 19, 2003
Abstract:
Light, oxygen, or voltage (LOV) domains constitute a new class of photoreceptor proteins that are sensitive to blue light through a noncovalently bound flavin chromophore. Blue-light absorption by the LOV2 domain initiates a photochemical reaction that results in formation of a long-lived covalent adduct between a cysteine and the flavin cofactor. We have applied ultrafast spectroscopy on the photoaccumulated covalent adduct state of LOV2 and find that, upon absorption of a near-UV photon by the adduct state, the covalent bond between the flavin and the cysteine is broken and the blue-light-sensitive ground state is regained on an ultrafast time scale of 100 ps. We thus demonstrate that the LOV2 domain is a reversible photochromic switch, which can be activated by blue light and deactivated by near-UV light.
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