The phocycle of a flavin-binding domain of the blue-light photoreceptor phototropin

Swartz, T.E., Corchnoy, S.B., Christie, J.M. , Lewis, J.W., Szundi, I., Briggs, W.R. and Bogomolni, R.A. (2001) The phocycle of a flavin-binding domain of the blue-light photoreceptor phototropin. Journal of Biological Chemistry, 276(39), pp. 36493-36500. (doi: 10.1074/jbc.M103114200)

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Abstract

The plant blue light receptor, phot1, a member of the phototropin family (1), is a plasma membrane-associated flavoprotein that contains two (∼110 amino acids) flavin-binding domains, LOV1 and LOV2, within its N terminus and a typical serine-threonine protein kinase domain at its C terminus. The LOV (light, oxygen, and voltage) domains belong to the PAS domain superfamily of sensor proteins. In response to blue light, phototropins undergo autophosphorylation. <i>E. coli</i>-expressed LOV domains bind riboflavin-5′-monophosphate, are photochemically active, and have major absorption peaks at 360 and 450 nm, with the 450 nm peak having vibronic structure at 425 and 475 nm. These spectral features correspond to the action spectrum for phototropism in higher plants. Blue light excitation of the LOV2 domain generates, in less than 30 ns, a transient ∼660 nm-absorbing species that spectroscopically resembles a flavin triplet state. This putative triplet state subsequently decays with a 4-μs time constant into a 390 nm-absorbing metastable form. The LOV2 domain (450 nm) recovers spontaneously with half-times of ∼50 s. It has been shown that the metastable species is likely a flavin-cysteine (Cys<sup>39</sup> thiol) adduct at the flavin C(4a) position. A LOV2C39A mutant generates the early photoproduct but not the adduct. Titrations of LOV2 using chromophore fluorescence as an indicator suggest that Cys<sup>39</sup> exists as a thiolate.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Christie, Professor John
Authors: Swartz, T.E., Corchnoy, S.B., Christie, J.M., Lewis, J.W., Szundi, I., Briggs, W.R., and Bogomolni, R.A.
Subjects:Q Science > QH Natural history > QH345 Biochemistry
Q Science > QK Botany
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Journal of Biological Chemistry
Journal Abbr.:J Biol Chem.
Publisher:American Society for Biochemistry and Molecular Biology, Inc.
ISSN:0021-9258
ISSN (Online):1083-351X

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