Structural Basis for the Photochemistry of α-Phycoerythrocyanin<sup>,</sup>

Schmidt, Marius; Patel, Anamika; Zhao, Yi; Reuter, W

doi:10.1021/bi061844j

Cited by 41 publications

(43 citation statements)

References 41 publications

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“…CD spectroscopy of photoactive biliproteins is most easily interpreted in terms of the facial disposition of the D-ring (22): negative CD for the long-wavelength transition is associated with the D-␣ f disposition, whereas positive CD corresponds to D-␤ f . This interpretation is consistent not only with all available phytochrome crystal structures (6,8,(16)(17)(18), but also with structural data for ␣-phycoerythrocyanin (␣-PEC), a phycobiliprotein that exhibits inversion of CD upon Z/E photoisomerization (20,30,31). Although confirmation will require crystallographic information on the Cph1 P fr state, we assign the P fr states of phytobilin phytochromes as D-␤ f , distinct from the D-␣ f P fr predicted for DrBphP and observed for PaBphP.…”

Section: Discussionsupporting

confidence: 85%

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Rockwell

Shang

Martin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

133

209

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Phytochromes are a widespread family of photosensory proteins first discovered in plants, which measure the ratio of red to far-red light to control many aspects of growth and development. Phytochromes interconvert between red-absorbing Pr and far-redabsorbing Pfr states via photoisomerization of a covalently-bound linear tetrapyrrole (bilin) chromophore located in a conserved photosensory core. From recent crystal structures of this core region, it has been inferred that the chromophore structures of Pr and Pfr are conserved in most phytochromes. Using circular dichroism spectroscopy and ab initio calculations, we establish that the Pfr states of the biliverdin-containing bacteriophytochromes DrBphP and PaBphP are structurally dissimilar from those of the phytobilincontaining cyanobacterial phytochrome Cph1. This conclusion is further supported by chromophore substitution experiments using semisynthetic bilin monoamides, which indicate that the propionate side chains perform different functional roles in the 2 classes of phytochromes. We propose that different directions of bilin D-ring rotation account for these distinct classes of red/far-red photochemistry.bilin amides ͉ biliprotein ͉ circular dichroism ͉ photoisomerization P hytochromes comprise a class of red/far-red biliprotein photoreceptors that regulate photomorphogenesis, shade avoidance, and development in higher plants (1, 2). Also found in bacteria and fungi, phytochromes characteristically photoconvert between red-absorbing P r and far-red-absorbing P fr states (3,4). Conversion between these 2 states involves Z/E photoisomerization of the 15/16 double bond of their linear tetrapyrrole (bilin) chromophores. Photosensory signaling by phytochromes relies on a conserved core comprising PAS (PER, ARNT, SIM), GAF (cGMP phosphodiesterase, adenylate cyclase, FhlA), and PHY (phytochrome-specific GAF-related) domains (5), with the bilin bound within a conserved pocket of the GAF domain (1, 6). The precise structure of the bilin chromophore, the nature of its covalent linkage to cysteine (Cys) side chains in the protein, and the location of those Cys residues vary among phytochromes (7), and 2 distinct subclasses can be distinguished on these grounds.Phytobilin-containing phytochromes, which include the plant (Phys) and cyanobacterial (Cph1) phytochromes, are found exclusively in oxygenic photosynthetic organisms. The chromophore precursor for these phytochromes is either phytochromobilin or phycocyanobilin (PCB), both of which possess reduced ethylidene-containing A-rings. For these phytochromes, covalent linkage forms between a GAF-domain Cys and the ␣-carbon of the A-ring ethylidene (Fig. S1 A). The much more widespread biliverdin-containing phytochromes (4), which include the bacteriophytochromes (BphPs) and fungal phytochromes, possess covalent linkages between a Cys residue upstream of the PAS domain and the ␤-carbon of the A-ring endo-vinyl group of biliverdin IX␣ (BV; Fig. S1B) (8). P r is commonly the thermally stable dark state for both classes of...

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Section: Discussionsupporting

confidence: 85%

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Rockwell

Shang

Martin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

133

209

View full text Add to dashboard Cite

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“…By comparison, superposition of the Pb and Pg crystal structures estimated a 165°D-ring flip (21,22). This 15Z to E isomerization is in agreement with the 15E photoproduct of PVB when bound to cyanobacterial photosynthetic antennae protein ␣-phycoerythrocyanin (31) and with the photoconversion mechanism proposed for a canonical phytochrome assembled with PCB (9). Photoconversion in solution also induced an ϳ71°swivel of the A ring based on the average of the five lowest energy NMR structures (Fig.…”

Section: Resultssupporting

confidence: 72%

Dynamic Structural Changes Underpin Photoconversion of a Blue/Green Cyanobacteriochrome between Its Dark and Photoactivated States

Cornilescu

Burgie

et al. 2014

Journal of Biological Chemistry

100

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Background: Phytochromes are photochromic bili-proteins vital to microbial and plant photoperception. Results: NMR spectroscopy generated three-dimensional structures of the photosensing module from a cyanobacterial variant in the dark and photoactivated states. Conclusion: Photoconversion involves thioether bond rupture, bilin isomerization and sliding, and increased protein disorder. Significance: Combined with crystallographic models, these paired NMR structures provide an unprecedented view into photoconversion of a phytochrome-type photoreceptor.

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“…Sequence alignment shows that all phytochromes contain aromatic residues at both positions: either Tyr or Phe at the position of Tyr-190 but only Tyr at the position of Tyr-163. Similar displacements of aromatic side chains around ring D have also been observed in the crystal structures of ␣-phycoerythrocyanin with its phycoviolobilin chromophore in the Z-and E-configurations (26). In Cph1, the equivalent Y176H mutant is unable to undergo photoconversion and is intensely fluorescent, with an emission maximum of approximately 650-670 nm (8).…”

Section: Of Ref 5)supporting

confidence: 71%

Crystal structure of Pseudomonas aeruginosa bacteriophytochrome: Photoconversion and signal transduction

Yang¹,

Kuk²,

Moffat

2008

Proc. Natl. Acad. Sci. U.S.A.

295

587

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Phytochromes are red-light photoreceptors that regulate light responses in plants, fungi, and bacteria via reversible photoconversion between red (Pr) and far-red (Pfr) light-absorbing states. Here we report the crystal structure at 2.9 Å resolution of a bacteriophytochrome from Pseudomonas aeruginosa with an intact, fully photoactive photosensory core domain in its darkadapted Pfr state. This structure reveals how unusual interdomain interactions, including a knot and an ''arm'' structure near the chromophore site, bring together the PAS (Per-ARNT-Sim), GAF (cGMP phosphodiesterase/adenyl cyclase/FhlA), and PHY (phytochrome) domains to achieve Pr/Pfr photoconversion. The PAS, GAF, and PHY domains have topologic elements in common and may have a single evolutionary origin. We identify key interactions that stabilize the chromophore in the Pfr state and provide structural and mutational evidence to support the essential role of the PHY domain in efficient Pr/Pfr photoconversion. We also identify a pair of conserved residues that may undergo concerted conformational changes during photoconversion. Modeling of the full-length bacteriophytochrome structure, including its output histidine kinase domain, suggests how local structural changes originating in the photosensory domain modulate interactions between long, crossdomain signaling helices at the dimer interface and are transmitted to the spatially distant effector domain, thereby regulating its histidine kinase activity.phytochrome ͉ photoreceptor

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Structural Basis for the Photochemistry of α-Phycoerythrocyanin^,

Cited by 41 publications

References 41 publications

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Dynamic Structural Changes Underpin Photoconversion of a Blue/Green Cyanobacteriochrome between Its Dark and Photoactivated States

Crystal structure of Pseudomonas aeruginosa bacteriophytochrome: Photoconversion and signal transduction

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Structural Basis for the Photochemistry of α-Phycoerythrocyanin,

Cited by 41 publications

References 41 publications

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Distinct classes of red/far-red photochemistry within the phytochrome superfamily

Dynamic Structural Changes Underpin Photoconversion of a Blue/Green Cyanobacteriochrome between Its Dark and Photoactivated States

Crystal structure of Pseudomonas aeruginosa bacteriophytochrome: Photoconversion and signal transduction

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Structural Basis for the Photochemistry of α-Phycoerythrocyanin^,