title: Searching for the mechanism of signalling by plant photoreceptor cryptochrome.
abstract: Even though the plant photoreceptors cryptochromes were discovered more than 20 years ago, the mechanism through which they transduce light signals to their partner molecules such as COP1 (Constitutive Photomorphogenic 1) or SPA1 (Suppressor of Phytochrome A) still remains to be established. We propose that a negative charge induced by light in the vicinity of the flavin chromophore initiates cryptochrome 1 signalling. This negative charge might expel the protein-bound ATP from the binding pocket, thereby pushing off the C-terminus that covers the ATP pocket in the dark state of the protein. This conformational change should allow for phosphorylation of previously inaccessible amino acids. A partially phosphorylated 'ESSSSGRR-VPE' fragment of the C-terminus could mimic the sequence of the transcription factor HY5 that is essential for binding to the negative regulator of photomorphogenesis COP1. HY5 release through competition for the COP1 binding site could represent the long-sought connection between light activation of cryptochrome and modulation of photomorphogenesis.
authors.affiliation: UMR-8221, CEA - Institut de Biologie et de Technologie de Saclay, CNRS, Université Paris Sud, 91191 Gif-sur-Yvette, France. Electronic address: pavel.muller@cea.fr.
authors.forename: Pavel
authors.initials: P
authors.lastname: Müller
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7238, Computational and Quantitative Biology, 75005 Paris, France; CNRS, UMR 7238, Computational and Quantitative Biology, 75006 Paris, France. Electronic address: jean-pierre.bouly@upmc.fr.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Bouly
mesh_terms: D056931:Cryptochromes / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D010944:Plants / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D056931:Cryptochromes; D010940:Plant Proteins; D014157:Transcription Factors
keywords: ATP; Constitutive Photomorphogenic 1; HY5; Photoreceptor; Plant cryptochrome; Signalling