Study of photostate-stabilizing mutants of the bacteriophytochrome from the plant pathogen Xanthomonas campestris (Póster)

GIULIANO T. ANTELO; SEBASTIÁN KLINKE; MAXIMILIANO SÁNCHEZ-LAMAS; VALERIA CONFORTE; FLORENCIA MALAMUD; FERNANDO A. GOLDBAUM; LISANDRO OTERO; HERNÁN R. BONOMI; JIMENA RINALDI

Paraná

Congreso; LIV Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2018

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Bacteriophytochromes(BphPs) are part of the phytochrome superfamily of photoreceptors. BphPs areproteins that bind biliverdin (BV) as their chromophore and typically presenttwo photostates:   primarily red-absorbing form (Pr) and afar-red-absorbing form (Pfr). We have recently shown that the BphP from theplant pathogen bacterium Xanthomonas campestris (XccBphP) modulates theinteraction with its host, and performed several biophysical studies showingthat XccBphP is a bathy-like phytochrome (Pfr-enriched equilibrium asground-state). Moreover, we have solved the 3D crystal structure of thefull-length protein in the Pr state (the first in photobiology). In order toevaluate the biological role of XccBphP in vivo and solve its structure in Pfrform, we have designed punctual and randomized mutants of XccBphP in conserved residueslinked to the photochemical behavior. By means of a UV-VIS spectroscopyprotocol designed for a rapid and precise characterization of these mutants, wehave characterized several mutants with different photochemical behavior,including one that stabilizes the Pfr. Several biophysical studies have beenmade with this mutant, including crystallogenesis and X-ray diffraction. Thelatter allowed us to obtain the first Pfr structure of a full-lengthphytochrome to compare it with the already solved Pr. Here, we show results ofall these experiments, as well as some preliminary work done in vivo. Weprovide new insights on the structural mechanisms involved in the light-inducedsignal transduction of phytochromes.