Unravelling the long-range signaling mechanism of bacteriophytochromes

RINALDI J; MROGINSKI, M.A.; BONOMI, H.R.; OTERO, L.H.; VELÁZQUEZ-ESCOBAR, F.; HILDEBRANDT, P.; KLINKE S; FERNÁNDEZ LÓPEZ, M.; GOLBAUM, F.A.

San Luis

Congreso; XII Reunión Annual de la Asociación Argentina de Cristalografía; 2016

Asociación Argentina de Cristalografía

Light-induced reactions allow organisms to adapt to different environmental factors. Bacteriophytochromes (BphPs) are light-sensing proteins found among photosynthetic and non-photosynthetic bacteria 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), and a C-terminal variable output module (OM). Although, several BphPs have been biophysically characterized, it is still not fully understood how structural changes are propagated from the PCM to the OM during the signal transduction event. Here we present the crystal structures of the PCM, and the PCM plus the OM (full-lengh version) of the BphP from the plant pathogen Xanthomonas campestris (XccBphP). In the crystals, the PCM was found to be in the Pfr state, while the full-lengh version showed a Pr state where resonance Raman spectroscopic and theoretical results indicate a ZZZssa and a ZZEssa chromophore configuration corresponding to a mixture of Pr and Meta-R state. The XccBphP quaternary assembly reveals a head-to-head dimer in which the OM contributes to the helical dimer interface. 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.