Disruption of the LOV-J alpha helix interaction activates phototropin kinase activity

Harper, S.M., Christie, J.M. and Gardner, K.H. (2004) Disruption of the LOV-J alpha helix interaction activates phototropin kinase activity. Biochemistry, 43(51), pp. 16184-16192. (doi: 10.1021/bi048092i)

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Light plays a crucial role in activating phototropins, a class of plant photoreceptors that are sensitive to blue and UV-A wavelengths. Previous studies indicated that phototropin uses a bound flavin mononucleotide (FMN) within its light−oxygen−voltage (LOV) domain to generate a protein−flavin covalent bond under illumination. In the C-terminal LOV2 domain of <i>Avena sativa</i> phototropin 1, formation of this bond triggers a conformational change that results in unfolding of a helix external to this domain called Jα [Harper, S. M., et al. (2003) Science 301, 1541−1545]. Though the structural effects of illumination were characterized, it was unknown how these changes are coupled to kinase activation. To examine this, we made a series of point mutations along the Jα helix to disrupt its interaction with the LOV domain in a manner analogous to light activation. Using NMR spectroscopy and limited proteolysis, we demonstrate that several of these mutations displace the Jα helix from the LOV domain independently of illumination. When placed into the full-length phototropin protein, these point mutations display constitutive kinase activation, without illumination of the sample. These results indicate that unfolding of the Jα helix is the critical event in regulation of kinase signaling for the phototropin proteins.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Christie, Professor John
Authors: Harper, S.M., Christie, J.M., and Gardner, K.H.
Subjects:Q Science > QH Natural history > QH345 Biochemistry
College/School:College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
Journal Name:Biochemistry
ISSN (Online):1520-4995
Published Online:26 November 2004

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