The Phot LOV2 Domain and Its Interaction with LOV1
Huimin Guo 1, Tilman Kottke 2, Peter Hegemann 3 and Bernhard Dick 1*
1 Institut für Physikalische und Theoretische Chemie, Universität Regensburg
2 Research Center Jülich
3 Institute of Biology, Humboldt Universität Berlin
* To whom correspondence should be addressed. E-mail: bernhard.dick{at}chemie.uni-regensburg.de.
Submitted on December 17, 2004
Revised on February 23, 2005
Accepted on 20 April 2005
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Abstract |
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Phot proteins are homologs of the blue-light receptor phototropin. We report a comparative study of the photocycles of the isolated, light-sensitive domains LOV1 and LOV2 from Chlamydomonas reinhardtii Phot protein, as well as the construct LOV1/2 containing both domains. Transient absorption measurements revealed a short lifetime of the LOV2-wt triplet state (500 ns), but a long lifetime (287 µs) of the triplet in the mutant LOV2-C250S in which the reactive cysteine is replaced by serine. For LOV1 in comparison, corresponding numbers of 800 ns and 4 µs for the two conformers in LOV1-wt, and 27 µs for LOV1-C57S have been reported. The triplet decay kinetics in the mixed domains LOV1/2-wt, LOV1/2-C57S, and LOV1/2-C250S can be analyzed as the superposition of the behavior of the corresponding single domains. The situation is different for the slow, thermal reaction of the photoadduct back to the dark form. Whereas the individual domains LOV1 and LOV2 show two decay components, the double domains LOV1/2-C57S and LOV1/2-C250S both show only a single component. The interaction of the two domains does therefore not manifest itself during the lifetime of the triplet states, but changes the decay behavior of the adduct states.
Key Words:
Blue-Light Photoreceptor, Chlamydomonas, LOV-domain, Photocycle, Phototropin
