Bases estructurales del sensado de luz en el fitopatógeno Xanthomonas campestris

JIMENA RINALDI

Rosario

Seminario; Seminario; 2022

CEFOBI

Phytochromes constitute a widespread photoreceptor family that typically interconverts between two photostatescalled Pr (red light–absorbing) and Pfr (far-red light–absorbing). The lack of full-length structures solved at the(near-)atomic level in both pure Pr and Pfr states leaves gaps in the structural mechanisms involved in the signaltransmission pathways during the photoconversion. Here, we present the crystallographic structures of threeversions from the plant pathogen Xanthomonas campestris virulence regulator XccBphP bacteriophytochrome,including two full-length proteins, in the Pr and Pfr states. The structures show a reorganization of the interactionnetworks within and around the chromophore-binding pocket, an -helix/-sheet tongue transition, and specificdomain reorientations, along with interchanging kinks and breaks at the helical spine as a result of the photoswitching,which subsequently affect the quaternary assembly. These structural findings, combined with multidisciplinarystudies, allow us to describe the signaling mechanism of a full-length bacterial phytochrome at the atomic level.