The structure of a complete phytochrome sensory module in the Pr ground state.

摘要: Phytochromes 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 phytochrome photoswitch is still unclear. Here, we report ground state structure complete sensory module Cph1 from cyanobacterium Synechocystis 6803. Although phycocyanobilin (PCB) chromophore attached to Cys-259 as expected, paralleling situation plant phytochromes but contrasting that bacteriophytochromes, ZZZssa conformation does not correspond expected Raman spectroscopy. We show PHY domain, previously considered unique phytochromes, structurally a member GAF (cGMP phosphodiesterase/adenylyl cyclase/FhlA) family. Indeed, tandem-GAF dumbbell revealed for modules remarkably similar regulatory domains cyclic nucleotide (cNMP) phosphodiesterases adenylyl cyclases. A feature long, tongue-like protrusion domain seals pocket stabilizes photoactivated far-red-absorbing (Pfr). The tongue carries conserved PRxSF motif, an arginine finger points into close ring D forming salt bridge with aspartate residue. present provides framework light-driven signal transmission phytochromes.