Engineering Escherichia coli to see light

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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“…Mutagenesis and assays of LacZ and the control of Cph8 (Cph1:EnvZ chimeric phytochrome, see ref. 48) are given in the SI Text.…”

Section: Methodsmentioning

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.

162

299

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“…PhyB and PIF interact after irradiation with red light and dissociate with exposure to far-red light (3). This system requires a chromophore, phycocyanobilin that is not naturally present in many organisms, including mammals (7,8). The tunable lightcontrolled interacting protein tags (TULIPs) make use of the blue light-sensing light-oxygen-voltage (LOV) domain and an engineered PDZ domain (9).…”

mentioning

confidence: 99%

Engineering an improved light-induced dimer (iLID) for controlling the localization and activity of signaling proteins

Guntas¹,

Hallett²,

Zimmerman³

et al. 2014

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

589

719

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The discovery of light-inducible protein-protein interactions has allowed for the spatial and temporal control of a variety of biological processes. To be effective, a photodimerizer should have several characteristics: it should show a large change in binding affinity upon light stimulation, it should not cross-react with other molecules in the cell, and it should be easily used in a variety of organisms to recruit proteins of interest to each other. To create a switch that meets these criteria we have embedded the bacterial SsrA peptide in the C-terminal helix of a naturally occurring photoswitch, the light-oxygen-voltage 2 (LOV2) domain from Avena sativa. In the dark the SsrA peptide is sterically blocked from binding its natural binding partner, SspB. When activated with blue light, the C-terminal helix of the LOV2 domain undocks from the protein, allowing the SsrA peptide to bind SspB. Without optimization, the switch exhibited a twofold change in binding affinity for SspB with light stimulation. Here, we describe the use of computational protein design, phage display, and high-throughput binding assays to create an improved light inducible dimer (iLID) that changes its affinity for SspB by over 50-fold with light stimulation. A crystal structure of iLID shows a critical interaction between the surface of the LOV2 domain and a phenylalanine engineered to more tightly pin the SsrA peptide against the LOV2 domain in the dark. We demonstrate the functional utility of the switch through lightmediated subcellular localization in mammalian cell culture and reversible control of small GTPase signaling.optogenetic tool | PER-ARNT-SIM domain | computational library | phage display | Rosetta molecular modeling suite

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“…Small size and modularity of these pathways have already made them a target for rewiring and synthetic application in prokaryotic cells (28)(29)(30) as well as Arabidopsis (31). There was also a report on functional complementation by a plant-derived HK in yeast (32).…”

mentioning

confidence: 98%

Transplantation of prokaryotic two-component signaling pathways into mammalian cells

Hansen

Mailand

Swaminathan

et al. 2014

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

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Significance Synthetic biology and genetic engineering would greatly benefit from engineered genetic elements that are orthogonal to the host in which they operate. Two-component signaling pathways are the prevalent signal processing modality in prokaryotes that is also found in low eukaryotes and plants but absent from vertebrate cells. Here we investigate whether the elements of prokaryotic two-component pathways are operational in mammalian cells. We find that the core biochemical processes are maintained, whereas the capacity to sense chemical ligands is diminished or obscured. We use the pathways for multiinput gene regulation and show that they can serve as a rich source of orthogonal building blocks for gene expression control in mammalian cells. Our findings open new avenues in synthetic circuit design.

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Engineering Escherichia coli to see light

Cited by 586 publications

References 8 publications

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

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

Engineering an improved light-induced dimer (iLID) for controlling the localization and activity of signaling proteins

Transplantation of prokaryotic two-component signaling pathways into mammalian cells

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