Structure of the Full-Length Bacteriophytochrome from the Plant Pathogen Xanthomonas campestris Provides Clues to its Long-Range Signaling Mechanism.

OTERO LH; RINALDI J; KLINKE S; VELÁZQUEZ-ESCOBAR F; MROGINSKI MA; FERNÁNDEZ LÓPEZ M; MALAMUD F; VOJNOV AA; HILDEBRANDT P; GOLDBAUM FA; BONOMI HR

JOURNAL OF MOLECULAR BIOLOGY

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016

0022-2836

Phytochromes constitute a major superfamily of lightsensingproteins that are reversiblyphotoconverted between a redabsorbing(Pr) and a farredabsorbing(Pfr) state.Bacteriophytochromes (BphPs) are found among photosynthetic and nonphotosyntheticbacteria, including pathogens. To date, several BphPs have beenbiophysically characterized. However, it is still not fully understood how structuralchanges are propagated from the photosensory module to the output module during thesignal transduction event. Most phytochromes share a common architecture consistingof an Nterminalphotosensor that includes the PAS2?GAF?PHY domain triad and a Cterminalvariable output module. Here we present the crystal structure of the fulllengthBphP from the plant pathogen Xanthomonas campestris pv. campestris (XccBphP)bearing its photosensor and its complete output module, a PAS9 domain. In the crystals,the protein was found to be in the Pr state, whereas diffraction data together withresonance Raman spectroscopic and theoretical results indicate a ZZZssa and a ZZEssachromophore configuration corresponding to a mixture of Pr and MetaRstate, theprecursor of Pfr. The XccBphP quaternary assembly reveals a headtoheaddimer inwhich the output module contributes to the helical dimer interface. The photosensor,which is shown to be a bathylikeBphP, is influenced in its dark reactions by the outputmodule. Our structural analyses suggest that the photoconversion between the Pr and Pfr states in the fulllengthXccBphP may involve changes in the relative positioning ofthe output module. This work contributes to understand the lightinducedstructuralchanges propagated from the photosensor to the output modules in phytochromesignaling.