Highly Conserved Residues Asp-197 and His-250 in Agp1 Phytochrome Control the Proton Affinity of the Chromophore and Pfr Formation

Stetten, David von; Seibeck, Sven; Michael, Norbert; Scheerer, Patrick; Mroginski, María Andrea; Murgida, Daniel H.; Krauß, Norbert; Heyn, Maarten P.; Hildebrandt, Peter; Borucki, Berthold; Lamparter, Tilman

doi:10.1074/jbc.m608878200

Cited by 108 publications

(244 citation statements)

References 35 publications

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“…RcaE thus combines bilin photoisomerization with a subsequent shift in the bilin pK a , using a protochromic triad of three key residues to drive the proton transfer that causes the shift between green and red absorption. Our results show that CBCRs need not share the behavior of phytochromes and phycobiliproteins, in which the bilin chromophore is always protonated under static conditions (10)(11)(12).…”

Section: Discussionmentioning

confidence: 84%

“…Tyr176 and His290 of Cph1, forming part of the pocket for the photoactive bilin Dring, are conserved in RcaE as Tyr187 and His285. Asp207 and His260 of Cph1 form hydrogen bonds with the bilin A-, B-, and C-rings, maintaining a high bilin pK a value of 9-11 (6,12). Sequence homology in the vicinity of Asp207 is poor between Cph1 and RcaE, but Glu217 of RcaE in this region is highly conserved among the green/red CBCRs.…”

Section: Resultsmentioning

confidence: 99%

“…This red/far-red photocycle is triggered by photoisomerization of the bilin 15,16-double bond between the 15Z and 15E configurations (7,8), with 15Z giving red absorption and 15E far-red absorption (4,6,9). In phytochromes, the conjugated π system of the bilin is protonated in both photostates, and this protonation is necessary to maintain the red and far-red absorption (10)(11)(12). Conserved GAF residues supply a hydrogen bond network to tune the chemical and spectral properties of the bilin (Fig.…”

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confidence: 99%

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Green/red cyanobacteriochromes regulate complementary chromatic acclimation via a protochromic photocycle

Hirose

Rockwell

Nishiyama

et al. 2013

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

143

265

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Cyanobacteriochromes (CBCRs) are cyanobacterial members of the phytochrome superfamily of photosensors. Like phytochromes, CBCRs convert between two photostates by photoisomerization of a covalently bound linear tetrapyrrole (bilin) chromophore. Although phytochromes are red/far-red sensors, CBCRs exhibit diverse photocycles spanning the visible spectrum and the near-UV (330-680 nm). Two CBCR subfamilies detect near-UV to blue light (330-450 nm) via a "two-Cys photocycle" that couples bilin 15Z/15E photoisomerization with formation or elimination of a second bilincysteine adduct. On the other hand, mechanisms for tuning the absorption between the green and red regions of the spectrum have not been elucidated as of yet. CcaS and RcaE are members of a CBCR subfamily that regulates complementary chromatic acclimation, in which cyanobacteria optimize light-harvesting antennae in response to green or red ambient light. CcaS has been shown to undergo a green/red photocycle: reversible photoconversion between a green-absorbing 15Z state ( 15Z P g ) and a red-absorbing 15E state ( 15E P r ). We demonstrate that RcaE from Fremyella diplosiphon undergoes the same photocycle and exhibits light-regulated kinase activity. In both RcaE and CcaS, the bilin chromophore is deprotonated as 15Z P g but protonated as 15E P r . This change of bilin protonation state is modulated by three key residues that are conserved in green/red CBCRs. We therefore designate the photocycle of green/red CBCRs a "protochromic photocycle," in which the dramatic change from green to red absorption is not induced by initial bilin photoisomerization but by a subsequent change in bilin protonation state.light sensing | phycobiliprotein | signal transduction | spectral tuning | two-component signaling P hytochrome photosensors initially were discovered in plants and later found in cyanobacteria, nonoxygenic photosynthetic bacteria, nonphotosynthetic bacteria, fungi, and algae (1, 2). These photoreceptors bind linear tetrapyrrole (bilin) chromophores within a conserved GAF (cGMP phosphodiesterase/adenylyl cyclase/FhlA) domain via a covalent thioether linkage to a conserved Cys residue (Fig. S1A)(3-6). Upon illumination, phytochromes reversibly convert between a red-absorbing dark state and a far-red-absorbing photoproduct. This red/far-red photocycle is triggered by photoisomerization of the bilin 15,16-double bond between the 15Z and 15E configurations (7,8), with 15Z giving red absorption and 15E far-red absorption (4, 6, 9). In phytochromes, the conjugated π system of the bilin is protonated in both photostates, and this protonation is necessary to maintain the red and far-red absorption (10-12). Conserved GAF residues supply a hydrogen bond network to tune the chemical and spectral properties of the bilin (Fig. S1B).* Cyanobacteriochromes (CBCRs) are widespread cyanobacterial photosensors with phytochrome-related GAF domains (1,2,13,14). Although CBCRs also convert between two photostates via bilin photoisomerization at C15, they exhibit much more spe...

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Section: Discussionmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Green/red cyanobacteriochromes regulate complementary chromatic acclimation via a protochromic photocycle

Hirose

Rockwell

Nishiyama

et al. 2013

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

143

265

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“…Along the GAF-tongue interface, further hydrogen bondings with conserved tongue residues in the kink region involving Trp-478 and Glu-480 (β20 helix) are likely to play a role in signal transduction. Although mutations at Asp-207 and homologous residues destabilize or prevent the formation of Pfr (44)(45)(46), mutation of its salt-bridge partner Arg-472 in Cph1 has little effect on Pr/Pfr absorbance properties and Pfr stability, even though this residue too is conserved. Its likely critical function is in initiating signal transduction, as implied by the loss of Pr/Pfr autokinase regulation in the full-length Arg-472-Ala holoprotein mutant (Fig.…”

Section: Resultsmentioning

confidence: 99%

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Song

Psakis

Lang

et al. 2011

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

160

299

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Phytochrome photoreceptors mediate light responses in plants and in many microorganisms. Here we report studies using 1 H-13 C magic-angle spinning NMR spectroscopy of the sensor module of cyanobacterial phytochrome Cph1. Two isoforms of the red-light absorbing Pr ground state are identified. Conclusive evidence that photoisomerization occurs at the C15-methine bridge leading to a β-facial disposition of the ring D is presented. In the far-red-light absorbing Pfr state, strong hydrogen-bonding interactions of the D-ring carbonyl group to Tyr-263 and of N24 to Asp-207 hold the chromophore in a tensed conformation. Signaling is triggered when Asp-207 is released from its salt bridge to Arg-472, probably inducing conformational changes in the tongue region. A second signal route is initiated by partner swapping of the B-ring propionate between Arg-254 and Arg-222.chromophore-protein interaction | signal transduction | solid-state NMR | photomorphogenesis P hytochrome was first demonstrated in plants as a red-lightdependent photoreceptor regulating numerous photomorphogenic processes (1, 2). Phytochromes are, however, also now known in photosynthetic prokaryotes including cyanobacteria (3, 4), nonphotosynthetic bacteria (5), and fungi (6). Generally, the phytochrome apoprotein binds an open-chain tetrapyrrole as a chromophore (7,8) to form the red-light absorbing Pr ground state (λ max ≈ 658 nm in case of cyanobacterial phytchrome Cph1 from Synechocystis 6803). Red light absorption photoactivates the molecule to form the photoactivated far-red-light absorbing Pfr state (λ max ≈ 702 nm for Cph1) via a series of intermediates (8-10). Photoactivation is thought to be initiated by a double bond isomerization of the chromophore (10, 11). Early NMR spectroscopic studies on proteolytic phytochrome fragments (12, 13) indicated that this isomerization occurs at the C15═C16 double bond (for numbering, see Fig. 1A), a geometrical change in line with vibrational spectroscopic investigations (14-16) and results from recent 13 C solid-state NMR (17, 18) in which the most significant changes during the light-triggered conversions are confined to rings C and D. Exact geometries of the chromophore in the Pr state have been resolved as periplanar ZZZssa configurations in bacteriophytochromes from Deinococcus radiodurans (19) and Rhodopseudomonas palustris (20) as well as in the more plant-phytochrome-like Cph1 from the cyanobacterium Synechocystis 6803 (21). On the other hand, the crystal structure of the unusual bacteriophytochrome PaBphP Pseudomonas aeruginosa (22) whose ground state is Pfr shows a ZZEssa conformation, consistent with the expected primary photochemistry at the C15═C16 double bond (Fig. 1 B vs. C). Very recently, however, Ulijasz et al. presented structural simulations based on liquid NMR data of a 20-kDa GAF (cGMP phosphodiesterase/ adenylyl cyclase/FhlA) domain fragment of "SyB-Cph1" phytochrome from the thermotolerant cyanobacterium Synechococcus OSB′ (23). Surprisingly, they concluded that photoisomerization occ...

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“…In all cases, protein variants lacking the histidine kinase module were used. Previous comparative studies of Agp1 revealed identical RR spectra for proteins including and lacking the kinase module (31,32).…”

Section: Methodsmentioning

confidence: 94%

Structure of the Biliverdin Cofactor in the Pfr State of Bathy and Prototypical Phytochromes

Salewski

Escobar

Kaminski

et al. 2013

Journal of Biological Chemistry

Self Cite

139

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Background:The Pr and Pfr parent states of prototypical and bathy bacteriophytochromes exhibit different thermal stabilities. Results: Unlike bathy phytochromes, the biliverdin cofactor of prototypical phytochromes displays distinct conformational heterogeneity in Pfr. Conclusion: This heterogeneity enables thermal Pfr to Pr conversion in prototypical phytochromes. Significance: Understanding thermal deactivation of the signaling Pfr state is essential for elucidating the molecular function of phytochromes.

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Highly Conserved Residues Asp-197 and His-250 in Agp1 Phytochrome Control the Proton Affinity of the Chromophore and Pfr Formation

Cited by 108 publications

References 35 publications

Green/red cyanobacteriochromes regulate complementary chromatic acclimation via a protochromic photocycle

Green/red cyanobacteriochromes regulate complementary chromatic acclimation via a protochromic photocycle

Two ground state isoforms and a chromophore D -ring photoflip triggering extensive intramolecular changes in a canonical phytochrome

Structure of the Biliverdin Cofactor in the Pfr State of Bathy and Prototypical Phytochromes

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