2vea
The complete sensory module of the cyanobacterial phytochrome Cph1 in the Pr-state.
Structural highlights
FunctionPHY1_SYNY3 Regulatory photoreceptor which exists in two forms that are reversibly interconvertible by light: the R form that absorbs maximally in the red region of the spectrum and the FR form that absorbs maximally in the far-red region. Has also a slight blue shift for the far-red maximum. Forms a two-component system with the rcp1 response regulator. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPhytochromes are red/far-red photochromic biliprotein photoreceptors, which in plants regulate seed germination, stem extension, flowering time, and many other light effects. However, the structure/functional basis of the phytochrome photoswitch is still unclear. Here, we report the ground state structure of the complete sensory module of Cph1 phytochrome from the cyanobacterium Synechocystis 6803. Although the phycocyanobilin (PCB) chromophore is attached to Cys-259 as expected, paralleling the situation in plant phytochromes but contrasting to that in bacteriophytochromes, the ZZZssa conformation does not correspond to that expected from Raman spectroscopy. We show that the PHY domain, previously considered unique to phytochromes, is structurally a member of the GAF (cGMP phosphodiesterase/adenylyl cyclase/FhlA) family. Indeed, the tandem-GAF dumbbell revealed for phytochrome sensory modules is remarkably similar to the regulatory domains of cyclic nucleotide (cNMP) phosphodiesterases and adenylyl cyclases. A unique feature of the phytochrome structure is a long, tongue-like protrusion from the PHY domain that seals the chromophore pocket and stabilizes the photoactivated far-red-absorbing state (Pfr). The tongue carries a conserved PRxSF motif, from which an arginine finger points into the chromophore pocket close to ring D forming a salt bridge with a conserved aspartate residue. The structure that we present provides a framework for light-driven signal transmission in phytochromes. The structure of a complete phytochrome sensory module in the Pr ground state.,Essen LO, Mailliet J, Hughes J Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14709-14. Epub 2008 Sep 17. PMID:18799745[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References | ||||||||||||||||||||
