Unravelling the long-range signaling mechanism of bacteriophytochromes (Comunicación Oral)

LISANDRO OTERO; SEBASTIÁN KLINKE; JIMENA RINALDI; FRANCISCO VELÁZQUEZ-ESCOBAR; MARÍA ANDREA MROGINSKI; PETER HILDEBRANDT; FERNANDO A. GOLDBAUM; HERNÁN BONOMI

Córdoba

Congreso; LII Reunión Anual SAIB; 2016

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Light-inducedreactions allow organisms to adapt to different environmental factors. Bacteriophytochromes(BphPs) are light-sensing proteins found among photosynthetic andnon-photosynthetic bacteria that are reversibly photoconverted between ared-absorbing (Pr) and a far-red-absorbing (Pfr) state. Most BphPs share acommon 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 thePCM to the OM during the photoconversion Pr-Pfr in the signal transductionevent. Here we present the crystal structures of the full-length BphP (PCM +OM) from the plant pathogen Xanthomonas campestris (XccBphP) and of itsisolated PCM. In the crystals, the full-length protein showed a Pr state whilethe PCM was found to be in the Pfr state. The quaternary assembly reveals ahead-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 constructis a monomer. Our structural analysis suggests that the long-range signaling inBphPs may involve a kink and a rotation of the OM position via a helical spinemovement during the photoconversion Pr-Pfr.