Type 2C protein phosphatases (PP2Cs) are vitally involved in abscisic acid (ABA) signaling. Here, we show that a synthetic growth inhibitor called pyrabactin functions as a selective ABA agonist. ...Pyrabactin acts through PYRABACTIN RESISTANCE 1 (PYR1), the founding member of a family of START proteins called PYR/PYLs, which are necessary for both pyrabactin and ABA signaling in vivo. We show that ABA binds to PYR1, which in turn binds to and inhibits PP2Cs. We conclude that PYR/PYLs are ABA receptors functioning at the apex of a negative regulatory pathway that controls ABA signaling by inhibiting PP2Cs. Our results illustrate the power of the chemical genetic approach for sidestepping genetic redundancy.
Rising temperatures and lessening fresh water supplies are threatening agricultural productivity and have motivated efforts to improve plant water use and drought tolerance. During water deficit, ...plants produce elevated levels of abscisic acid (ABA), which improves water consumption and stress tolerance by controlling guard cell aperture and other protective responses. One attractive strategy for controlling water use is to develop compounds that activate ABA receptors, but agonists approved for use have yet to be developed. In principle, an engineered ABA receptor that can be activated by an existing agrochemical could achieve this goal. Here we describe a variant of the ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) that possesses nanomolar sensitivity to the agrochemical mandipropamid and demonstrate its efficacy for controlling ABA responses and drought tolerance in transgenic plants. Furthermore, crystallographic studies provide a mechanistic basis for its activity and demonstrate the relative ease with which the PYR1 ligand-binding pocket can be altered to accommodate new ligands. Thus, we have successfully repurposed an agrochemical for a new application using receptor engineering. We anticipate that this strategy will be applied to other plant receptors and represents a new avenue for crop improvement.
Since the proposal of Anfinsen’s thermodynamic hypothesis in 1963, our understanding of protein folding and dynamics has gained significant appreciation of its nuance and complexity. Intrinsically ...disordered proteins, chameleonic sequences, morpheeins, and metamorphic proteins have broadened the protein folding paradigm. Here, we discuss noncanonical protein folding patterns, with an emphasis on metamorphic proteins, and we review known metamorphic proteins that occur naturally and that have been engineered in the laboratory. Finally, we discuss research areas surrounding metamorphic proteins that are primed for future exploration, including evolution, drug discovery, and the quest for previously unrecognized metamorphs. As we enter an age where we are capable of complex bioinformatic searches and de novo protein design, we are primed to search for previously unrecognized metamorphic proteins and to design our own metamorphs to act as targeted, switchable drugs; biosensors; and more.
Metamorphic proteins are single amino acid sequences that reversibly interconvert between multiple, dramatically different native structures, often with distinct functions. Since the discovery of the ...first metamorphic proteins in the early 2000s, several additional metamorphic proteins have been identified, and it was suggested that up to 4% of proteins in the PDB may switch folds. Metamorphic proteins have been found to share common features such as marginal thermostability and inconsistencies in predicted secondary structures. Outstanding challenges in the field include the search for more metamorphic proteins and the design of new proteins that switch folds. Identification of novel metamorphic proteins in nature will improve therapeutic targeting of fold-switching proteins involved in human pathology and will enhance the design of protein-based therapies. Designed fold switching proteins have applications as biosensors, molecular switches, molecular machines, and self-assembling systems.
•Metamorphic proteins exhibit marginal thermostability, spontaneous unfolding, and structural dissimilarity.•Naturally occurring metamorphic proteins are difficult to detect and are likely underrepresented in the Protein Data Bank.•Identification of new metamorphic proteins, e.g. from discordant structure predictions, may lead to therapeutic advances.•De novo design of fold switching proteins as biosensors, molecular switches, or other uses is an area of active research.
Human cytomegalovirus (HCMV) is a major pathogen in immunocompromised patients. The UL146 gene exists as 14 diverse genotypes among clinical isolates, which encode 14 different CXC chemokines. One ...genotype (vCXCL1GT1) is a known agonist for CXCR1 and CXCR2, while two others (vCXCL1GT5 and vCXCL1GT6) lack the ELR motif considered crucial for CXCR1 and CXCR2 binding, thus suggesting another receptor targeting profile. To determine the receptor target for vCXCL1GT5, the chemokine was probed in a G protein signaling assay on all 18 classical human chemokine receptors, where CXCR2 was the only receptor being activated. In addition, vCXCL1GT5 recruited β-arrestin in a BRET-based assay and induced migration in a chemotaxis assay through CXCR2, but not CXCR1. In contrast, vCXCL1GT1 stimulated G protein signaling, recruited β-arrestin and induced migration through both CXCR1 and CXCR2. Both vCXCL1GT1 and vCXCL1GT5 induced equally potent and efficacious migration of neutrophils, and ELR vCXCL1GT4 and non-ELR vCXCL1GT6 activated only CXCR2. In contrast to most human chemokines, the 14 UL146 genotypes have remarkably long C-termini. Comparative modeling using Rosetta showed that each genotype could adopt the classic chemokine core structure, and predicted that the extended C-terminal tail of several genotypes (including vCXCL1GT1, vCXCL1GT4, vCXCL1GT5, and vCXCL1GT6) forms a novel β-hairpin not found in human chemokines. Secondary NMR shift and TALOS+ analysis of vCXCL1GT1 supported the existence of two stable β-strands. C-terminal deletion of vCXCL1GT1 resulted in a non-functional protein and in a shift to solvent exposure for tryptophan residues likely due to destabilization of the chemokine fold. The results demonstrate that non-ELR chemokines can activate CXCR2 and suggest that the UL146 chemokines have unique C-terminal structures that stabilize the chemokine fold. Increased knowledge of the structure and interaction partners of the chemokine variants encoded by UL146 is key to understanding why circulating HCMV strains sustain 14 stable genotypes.
Evolution of fold switching in a metamorphic protein Dishman, Acacia F; Tyler, Robert C; Fox, Jamie C ...
Science (American Association for the Advancement of Science),
01/2021, Letnik:
371, Številka:
6524
Journal Article
Recenzirano
Odprti dostop
Metamorphic proteins switch between different folds, defying the protein folding paradigm. It is unclear how fold switching arises during evolution. With ancestral reconstruction and nuclear magnetic ...resonance, we studied the evolution of the metamorphic human protein XCL1, which has two distinct folds with different functions, making it an unusual member of the chemokine family, whose members generally adopt one conserved fold. XCL1 evolved from an ancestor with the chemokine fold. Evolution of a dimer interface, changes in structural constraints and molecular strain, and alteration of intramolecular protein contacts drove the evolution of metamorphosis. Then, XCL1 likely evolved to preferentially populate the noncanonical fold before reaching its modern-day near-equal population of folds. These discoveries illuminate how one sequence has evolved to encode multiple structures, revealing principles for protein design and engineering.
Abscisic acid (ABA) is an essential molecule in plant abiotic stress responses. It binds to soluble pyrabactin resistance1/PYR1-like/regulatory component of ABA receptor receptors and stabilizes them ...in a conformation that inhibits clade A type II C protein phosphatases; this leads to downstream SnRK2 kinase activation and numerous cellular outputs. We previously described the synthetic naphthalene sulfonamide ABA agonist pyrabactin, which activates seed ABA responses but fails to trigger substantial responses in vegetative tissues in Arabidopsis thaliana . Here we describe quinabactin, a sulfonamide ABA agonist that preferentially activates dimeric ABA receptors and possesses ABA-like potency in vivo. In Arabidopsis , the transcriptional responses induced by quinabactin are highly correlated with those induced by ABA treatments. Quinabactin treatments elicit guard cell closure, suppress water loss, and promote drought tolerance in adult Arabidopsis and soybean plants. The effects of quinabactin are sufficiently similar to those of ABA that it is able to rescue multiple phenotypes observed in the ABA-deficient mutant aba2 . Genetic analyses show that quinabactin’s effects in vegetative tissues are primarily mediated by dimeric ABA receptors. A PYL2-quinabactin-HAB1 X-ray crystal structure solved at 1.98-Å resolution shows that quinabactin forms a hydrogen bond with the receptor/PP2C “lock” hydrogen bond network, a structural feature absent in pyrabactin-receptor/PP2C complexes. Our results demonstrate that ABA receptors can be chemically controlled to enable plant protection against water stress and define the dimeric receptors as key targets for chemical modulation of vegetative ABA responses.
Drought causes crop losses worldwide, and its impact is expected to increase as the world warms. This has motivated the development of small-molecule tools for mitigating the effects of drought on ...agriculture. We show here that current leads are limited by poor bioactivity in wheat, a widely grown staple crop, and in tomato. To address this limitation, we combined virtual screening, x-ray crystallography, and structure-guided design to develop opabactin (OP), an abscisic acid (ABA) mimic with up to an approximately sevenfold increase in receptor affinity relative to ABA and up to 10-fold greater activity in vivo. Studies in
reveal a role of the type III receptor
for the antitranspirant efficacy of OP. Thus, virtual screening and structure-guided optimization yielded newly discovered agonists for manipulating crop abiotic stress tolerance and water use.
Metamorphic protein folding as evolutionary adaptation Dishman, Acacia F.; Volkman, Brian F.
Trends in biochemical sciences (Amsterdam. Regular ed.),
August 2023, 2023-08-00, 20230801, Letnik:
48, Številka:
8
Journal Article
Recenzirano
Proteins are generally presumed to fold into a single native-state structure.Some proteins clearly break the ‘one sequence, one fold’ rule.A metamorphic protein switches between two native, folded ...structures that differ significantly from each other.Evolutionary aspects of metamorphic proteins can be studied in multiple ways, including the resurrection of extinct ancestral versions.Emerging evidence suggests that metamorphic protein folding is selected for during evolution.
Metamorphic proteins switch reversibly between multiple distinct, stable structures, often with different functions. It was previously hypothesized that metamorphic proteins arose as intermediates in the evolution of a new fold – rare and transient exceptions to the ‘one sequence, one fold’ paradigm. However, as described herein, mounting evidence suggests that metamorphic folding is an adaptive feature, preserved and optimized over evolutionary time as exemplified by the NusG family and the chemokine XCL1. Analysis of extant protein families and resurrected protein ancestors demonstrates that large regions of sequence space are compatible with metamorphic folding. As a category that enhances biological fitness, metamorphic proteins are likely to employ fold switching to perform important biological functions and may be more common than previously thought.
The chemokine network is comprised of a family of signal proteins that encode messages for cells displaying chemokine G-protein coupled receptors (GPCRs). The diversity of effects on cellular ...functions, particularly directed migration of different cell types to sites of inflammation, is enabled by different combinations of chemokines activating signal transduction cascades on cells displaying a combination of receptors. These signals can contribute to autoimmune disease or be hijacked in cancer to stimulate cancer progression and metastatic migration. Thus far, three chemokine receptor-targeting drugs have been approved for clinical use: Maraviroc for HIV, Plerixafor for hematopoietic stem cell mobilization, and Mogalizumab for cutaneous T-cell lymphoma. Numerous compounds have been developed to inhibit specific chemokine GPCRs, but the complexity of the chemokine network has precluded more widespread clinical implementation, particularly as anti-neoplastic and anti-metastatic agents. Drugs that block a single signaling axis may be rendered ineffective or cause adverse reactions because each chemokine and receptor often have multiple context-specific functions. The chemokine network is tightly regulated at multiple levels, including by atypical chemokine receptors (ACKRs) that control chemokine gradients independently of G-proteins. ACKRs have numerous functions linked to chemokine immobilization, movement through and within cells, and recruitment of alternate effectors like β-arrestins. Atypical chemokine receptor 1 (ACKR1), previously known as the Duffy antigen receptor for chemokines (DARC), is a key regulator that binds chemokines involved in inflammatory responses and cancer proliferation, angiogenesis, and metastasis. Understanding more about ACKR1 in different diseases and populations may contribute to the development of therapeutic strategies targeting the chemokine network.
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