Crystal structure of a full-length bacteriophytochrome

OTERO, LISANDRO HORACIO; GOLDBAUM, FERNANDO A.; RINALDI, JIMENA; KLINKE, SEBASTIÁN; BONOMI, HERNAN R.

San Luis

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

Asociación Argentina de Cristalografía

Phytochromes give rise to the largest photosensor family known to date. Plant, cyanobacterial, fungal and bacterial phytochromes share a canonical architecture consisting of an N-terminal photosensory module (PAS2-GAF-PHY domains) and a C-terminal variable output module [1]. To date, several phytochromes have been structurally characterized, but none of them include a full-length version. The bacterium Xanthomonas campestris pv. campestris, a worldwide agricultural pathogen, codes for a single bacteriophytochrome (XccBphP) that has this canonical architecture, bearing a C-terminal PAS9 domain as the output module. Fulllength XccBphP was cloned, expressed and purified to homogeneity by nickel-NTA affinity and size-exclusion chromatography and was then crystallized at room temperature bound to its cofactor biliverdin. A complete native X-ray diffraction data set was collected to a maximum resolution of 3.25 Å. The crystals belonged to space group P43212, with unit-cell parameters a = b = 103.94, c = 344.57 Å [2]. The structure was solved by molecular replacement showing a Pr state (Fig 1) [3]. The XccBphP quaternary assembly reveals a head-to-head dimer in which the output module contributes to the helical dimer interface. This work contributes to understand the light-induced structural changes propagated from the photosensor to the output modules in full-length phytochromes signaling.