Photodynamics of blue-light-regulated phosphodiesterase BlrP1 protein from Klebsiella pneumoniae and its photoreceptor BLUF domain.
Abstract:
The BlrP1 protein from the enteric bacterium Klebsiella pneumoniae consists of a BLUF and an EAL domain
and may activate c-di-GMP phosphodiesterase by blue-light. The full-length protein, BlrP1, and its BLUF
domain, BlrP1_BLUF, are characterized by optical absorption and emission spectroscopy. The cofactor
FAD in its oxidized redox state (FADox) is brought from the dark-adapted receptor state to the 10-nm
red-shifted putative signalling state by violet light exposure. The recovery to the receptor state occurs
with a time constant of about 1 min. The quantum yield of signalling state formation is about 0.17 for
BlrP1_BLUF and about 0.08 for BlrP1. The fluorescence efficiency of the FADox cofactor is small due to
photo-induced reductive electron transfer. Prolonged light exposure converts FADox in the signalling state
to the fully reduced hydroquinone form FADredH and causes low-efficient chromophore release with
subsequent photo-degradation. The photo-cycle and photo-reduction dynamics in the receptor state
and in the signalling state are discussed.
