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Lyophilization Reveals a Multitude of Structural Conformations in the Chromophore of a Cph2-like Phytochrome
journal contribution
posted on 2020-08-06, 13:03 authored by Yunmi Kim, Qian-Zhao Xu, Kai-Hong Zhao, Wolfgang Gärtner, Jörg Matysik, Chen SongCyanobacteria
sense and respond to various colors of light employing
a large number of bilin-based phytochrome-like photoreceptors. All2699
from Nostoc 7120 has three consecutive GAF domains
with GAF1 and GAF3 binding a phycocyanobilin chromophore. GAF1, even
when expressed independently, can be photoconverted between red-absorbing
Pr and far-red-absorbing Pfr states, while the nonphotosensory GAF2
domain is structurally and functionally homologous to the PHY domains
in canonical and Cph2-like phytochromes. Here, we characterize possible
bilin chromophore conformers using solid-state NMR spectroscopy on
the two lyophilized All2699 samples (GAF1-only and GAF1–PHY
constructs). On the basis of complete 1H, 13C, and 15N assignments for the chromophore obtained on
the two Pr lyophilizates, multiple static conformations of the chromophore
in both cases are identified. Moreover, most atoms of the chromophore
in the bidomain sample show only subtle changes in the mean chemical
shifts relative to those in frozen solution (FS), indicating an optimized
interaction of the GAF2 domain with the GAF1-bound chromophore. Our
results confirm the conservation of key chromophore–protein
interactions and the photoreversibility in both All2699 lyophilizates,
offering the possibility to investigate conformational distributions
of the heterogeneous chromophore and its functional consequences in
phytochromes and other bilin-dependent photoreceptors intractable
by the solid-state NMR technique as FSs.
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Keywords
GAF 2 domain2699 lyophilizatesGAF 1optimized interactionNMR technique13 CPHY domainsNMR spectroscopyGAF domainsGAF 3 bindingStructural Conformationsphycocyanobilin chromophorenonphotosensory GAF 2 domainNostoc 7120GAF 1-bound chromophore15 N assignmentsGAF 1-onlyFSbilin-based phytochrome-like photor...far-red-absorbing Pfr statesPr lyophilizatesCph 2-like Phytochrome Cyanobacteri...1 Hred-absorbing Prchemical shiftsbilin chromophore conformersbidomain sample show2699 samplesCph 2-like phytochromesbilin-dependent photoreceptors
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