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Mutational analysis of phototropin 1 provides insights into the mechanism underlying LOV2 signal transmission.

Jones, Matthew A and Feeney, Kevin A and Kelly, Sharon M and Christie, John M (2007) 'Mutational analysis of phototropin 1 provides insights into the mechanism underlying LOV2 signal transmission.' J Biol Chem, 282 (9). 6405 - 6414. ISSN 0021-9258

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Abstract

Phototropins (phot1 and phot2) are blue light-activated serine/threonine protein kinases that elicit a variety of photoresponses in plants. Light sensing by the phototropins is mediated by two flavin mononucleotide (FMN)-binding domains, designated LOV1 and LOV2, located in the N-terminal region of the protein. Exposure to light results in the formation of a covalent adduct between the FMN chromophore and a conserved cysteine residue within the LOV domain. LOV2 photoexcitation is essential for phot1 function in Arabidopsis and is necessary to activate phot1 kinase activity through light-induced structural changes within a conserved alpha-helix situated C-terminal to LOV2. Here we have used site-directed mutagenesis to identify further amino acid residues that are important for phot1 activation by light. Mutagenesis of bacterially expressed LOV2 and full-length phot1 expressed in insect cells indicates that perturbation of the conserved salt bridge on the surface of LOV2 does not play a role in receptor activation. However, mutation of a conserved glutamine residue (Gln(575)) within LOV2, reported previously to be required to propagate structural changes at the LOV2 surface, attenuates light-induced autophosphorylation of phot1 expressed in insect cells without compromising FMN binding. These findings, in combination with double mutant analyses, indicate that Gln(575) plays an important role in coupling light-driven cysteinyl adduct formation from within LOV2 to structural changes at the LOV2 surface that lead to activation of the C-terminal kinase domain.

Item Type: Article
Uncontrolled Keywords: Animals, Arabidopsis, Arabidopsis Proteins, Biological Clocks, Cell Line, Cryptochromes, Cysteine, DNA Mutational Analysis, Flavin Mononucleotide, Flavoproteins, Glutamine, Light Signal Transduction, Mutagenesis, Site-Directed, Transfection
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Biological Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 12 Jan 2013 11:46
Last Modified: 28 Mar 2018 17:15
URI: http://repository.essex.ac.uk/id/eprint/5085

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