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

Jones, M. A. , Feeney, K. A., Kelly, S. M. and Christie, J. M. (2007) Mutational analysis of phototropin 1 provides insights into the mechanism underlying LOV2 signal transmission. Journal of Biological Chemistry, 282(9), pp. 6405-6414. (doi: 10.1074/jbc.M605969200) (PMID:17164248)

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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 α-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<sup>575</sup>) 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<sup>575</sup> 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:Articles
Glasgow Author(s) Enlighten ID:Kelly, Dr Sharon and Jones, Dr Matt and Christie, Professor John
Authors: Jones, M. A., Feeney, K. A., Kelly, S. M., and Christie, J. M.
Subjects:Q Science > QH Natural history > QH345 Biochemistry
College/School:College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
Journal Name:Journal of Biological Chemistry
Journal Abbr.:J Biol Chem.
Publisher:American Society for Biochemistry and Molecular Biology, Inc.
ISSN (Online):1083-351X
Published Online:12 December 2006

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