Heterogeneous Photodynamics of the Pfr State in the Cyanobacterial Phytochrome Cph1
نویسندگان
چکیده
Femtosecond photodynamics of the Pfr form of the red/far-red phytochrome N-terminal PAS-GAF-PHY photosensory core module of the cyanobacterial phytochrome Cph1 (termed Cph1Δ) from Synechocystis were resolved with visible broadband transient absorption spectroscopy. Multiphasic generation dynamics via global target analysis revealed parallel evolution of two pathways with distinct excited- and ground-state kinetics. These measurements resolved two subpopulations: a majority subpopulation with fast excited-state decay and slower ground-state dynamics, corresponding to previous descriptions of Pfr dynamics, and a minority subpopulation with slower excited-state decay and faster ground-state primary dynamics. Both excited-state subpopulations generated the isomerized, red-shifted Lumi-Ff photoproduct (715 nm); subsequent ground-state evolution to a blue-shifted Meta-Fr population (635 nm) proceeded on 3 ps and 1.5 ns time scales for the two subpopulations. Meta-Fr was spectrally similar to a recently described photoinactive fluorescent subpopulation of Pr ((Fluor)Pr). Thus, the reverse Pfr to Pr photoconversion of Cph1Δ involves minor structural deformation of Meta-Fr to generate the fluorescent, photochemically refractory form of Pr, with slower subsequent equilibration with the photoactive Pr subpopulation ((Photo)Pr).
منابع مشابه
Dynamic Inhomogeneity in the Photodynamics of Cyanobacterial Phytochrome Cph1
Phytochromes are widespread red/far-red photosensory proteins well known as critical regulators of photomorphogenesis in plants. It is often assumed that natural selection would have optimized the light sensing efficiency of phytochromes to minimize nonproductive photochemical deexcitation pathways. Surprisingly, the quantum efficiency for the forward Pr-to-Pfr photoconversion of phytochromes s...
متن کاملLight-induced chromophore activity and signal transduction in phytochromes observed by 13C and 15N magic-angle spinning NMR.
Both thermally stable states of phytochrome, Pr and Pfr, have been studied by (13)C and (15)N cross-polarization (CP) magic-angle spinning (MAS) NMR using cyanobacterial (Cph1) and plant (phyA) phytochrome sensory modules containing uniformly (13)C- and (15)N-labeled bilin chromophores. Two-dimensional homo- and heteronuclear experiments allowed most of the (13)C chemical shifts to be assigned ...
متن کاملTyrosine 263 in cyanobacterial phytochrome Cph1 optimizes photochemistry at the prelumi-R→lumi-R step.
We report a low-temperature fluorescence spectroscopy study of the PAS-GAF-PHY sensory module of Cph1 phytochrome, its Y263F mutant (both with known 3D structures) as well as Y263H and Y263S to connect their photochemical parameters with intramolecular interactions. None of the holoproteins showed photochemical activity at low temperature, and the activation barriers for the Pr→lumi-R photoreac...
متن کاملPhytochrome three-dimensional structures and functions.
The complete three-dimensional sensory module structures of the Pr ground state of Synechocystis 6803 Cph1 and the unusual Pfr ground state of the bacteriophytochrome PaBphP (PDB codes 2VEA and 3C2W respectively) have now been solved, revealing an asymmetrical dumbbell form made up of a PAS (Period/ARNT/Singleminded)-GAF (cGMP phosphodiesterase/adenylate cyclase/FhlA) bidomain carrying the chro...
متن کاملConformational heterogeneity of the Pfr chromophore in plant and cyanobacterial phytochromes
Phytochromes are biological photoreceptors that can be reversibly photoconverted between a dark and photoactivated state. The underlying reaction sequences are initiated by the photoisomerization of the tetrapyrrole cofactor, which in plant and cyanobacterial phytochromes are a phytochromobilin (PΦB) and a phycocyanobilin (PCB), respectively. The transition between the two states represents an ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره 53 شماره
صفحات -
تاریخ انتشار 2014