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Abstract: |
Photoactive yellow protein (PYP), a small
(~15,000 mol. wt.) water soluble blue light sensor, is a member
of a superfamily of PAS domain containing sensor proteins, and
is the structural prototype for over 5,000 known PAS domain
containing sensor proteins found throughout the evolutionary
tree. PYP is a blue light sensor, however, the PAS superfamily
is not restricted to light sensing, and depending on species
functions can range from oxygen, electric field and redox
sensing to small molecule sensing (for example, a wide range of
small organic molecules and metabolites). The functional
diversity of PAS domains is an outstanding example of the use of
a common structural motif, which adapted through evolution to
address the specific metabolic needs of a specific organism. PYP
undergoes a photoisomerization (trans p-hydroxy cinnamic
acid to cis) in ~3 ps, that initiates a series of
structural changes (photocycle) leading to the lit or signaling
state, which then activates a response regulator leading to
function. The lit state spontaneously reverts to the dark state
to complete the photocyclye. The formation of the lit state is
coupled with a major conformational change. Many of the PAS
domain containing sensor proteins are complex consisting of two
or more interacting domains.
A major focus of our work is on a blue-red light
sensing protein, called Ppr, which contains PYP,
bacteriophytochrome and histidine kinase domain, that
phosphorylates a transcriptional regulator when activated, which
turns on the expression of a polyketide synthase. Our goal is to
characterize the transient structural changes leading to the lit
state, and the mechanism by which the PYP, Bph and histidine
kinase interact leading to the light activation of the kinase.
Photoactive Yellow Protein: A Prototypic PAS
Domain Sensory Protein and Development of a Common Mechanism for
the Two-Component Regulatory Family. M. A. Cusanovich and T. E.
Meyer, Biochem. 42, 4759-70 (2003).
The Photoactivated PYP Domain of
Rhodospirillum centenum Ppr Accelerates Recovery of the
Bacteriophytochrome Domain After White Light Illumination.‘
John A. Kyndt, John C. Fitch, Terry E. Meyer, and Michael A.
Cusanovich, Biochem 46, 8256-62 (2007). |