Unravelling the long-range signaling mechanism of bacteriophytochromes

RINALDI, JIMENA; FERNÁNDEZ LÓPEZ, MARÍA; BONOMI, HERNAN R.; KLINKE, SEBASTIÁN; MROGINSKI, MARÍA ANDREA; OTERO, LISANDRO HORACIO; GOLDBAUM, FERNANDO A.; VELÁZQUEZ-ESCOBAR, FRANCISCO; HILDEBRANDT, PETER

Cordoba

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

Argentine Society for Biochemistry and Molecular Biology

Light-induced reactions allow organisms to adapt to different environmental factors. Bacteriophytochromes(BphPs) are light-sensing proteins found among photosynthetic and non-photosyntheticbacteria that are reversibly photoconverted between a red-absorbing (Pr) and a far-red-absorbing (Pfr) state. Most BphPs share a common architecture consisting of an N-terminal photosensor core module (PCM), which detects the light signal, and a C-terminal variable output module (OM), responsible for transducing this information into a biological effect. To date, it is still not fully understood how structural changes are propagated from the PCM to the OM during the photoconversion Pr-Pfr in the signal transduction event. Here we present the crystal structures of the full-lengh BphP (PCM + OM) from the plant pathogen Xanthomonas campestris (XccBphP) and of its isolated PCM. In the crystals,the full-lengh protein showed a Pr state while the PCM was found to be in the Pfr state. The quaternary assembly  reveals a head-to-head dimer in which the OM contributes to the helical dimer interface. In solution,the full-length version behaves as a dimer while the PCM construct is a monomer.Our structural analysis suggest that the long-range signaling in BphPs may involve a kink and a rotation of the OM position via a helical spine movement during the photoconversion Pr-Pfr.