An Ancient P-Loop GTPase in Rice Is Regulated by a Higher Plant-specific Regulatory Protein

Cheung, Ming-Yan; Xue, Yan; Zhou, Liang; Li, Man-Wah; Sun, Samuel S. M.; Lam, Hon‐Ming

doi:10.1074/jbc.m110.172080

Cited by 39 publications

(106 citation statements)

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“…Only GTP, but not ATP, could compete with Mant-GTP to bind to GST-OsYchF1-G4′. In contrast, similar experiments using the wild-type OsYchF1 showed competition by both GTP and ATP (12). Together, our results indicate that the noncanonical G4 motif in the native OsYchF1 is essential for ATP binding.…”

Section: Resultsmentioning

confidence: 43%

“…We previously established that OsYchF1 could hydrolyze both ATP and GTP (11,12). To understand the structural basis of nucleotide recognition, we compared the structures of OsYchF1 cocrystallized with AMPPNP and GMPPNP at pH 7.5 and at pH 8.0, respectively (Table S1 and Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We previously showed that the ectopic expression of OsYchF1 in Arabidopsis thaliana increases the sensitivity of the transgenic plants toward the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 (Pst DC3000) (12). Could the ability to bind and hydrolyze ATP have to do with its negative role in plant disease resistance?…”

Section: Resultsmentioning

confidence: 99%

“…The human YchF homolog hOLA1 suppresses cellular oxidative responses (9) but enhances heat shock responses (10). In plants, we have shown that rice (OsYchF1) and Arabidopsis (AtYchF1) YchF proteins function as negative regulators in both abiotic stress responses (11) and plant-defense responses (12).…”

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confidence: 99%

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ATP binding by the P-loop NTPase OsYchF1 (an unconventional G protein) contributes to biotic but not abiotic stress responses

Cheung

Miao

et al. 2016

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

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G proteins are involved in almost all aspects of the cellular regulatory pathways through their ability to bind and hydrolyze GTP. The YchF subfamily, interestingly, possesses the unique ability to bind both ATP and GTP, and is possibly an ancestral form of G proteins based on phylogenetic studies and is present in all kingdoms of life. However, the biological significance of such a relaxed ligand specificity has long eluded researchers. Here, we have elucidated the different conformational changes caused by the binding of a YchF homolog in rice (OsYchF1) to ATP versus GTP by X-ray crystallography. Furthermore, by comparing the 3D relationships of the ligand position and the various amino acid residues at the binding sites in the crystal structures of the apo-bound and ligand-bound versions, a mechanism for the protein's ability to bind both ligands is revealed. Mutation of the noncanonical G4 motif of the OsYchF1 to the canonical sequence for GTP specificity precludes the binding/hydrolysis of ATP and prevents OsYchF1 from functioning as a negative regulator of plant-defense responses, while retaining its ability to bind/hydrolyze GTP and its function as a negative regulator of abiotic stress responses, demonstrating the specific role of ATP-binding/hydrolysis in disease resistance. This discovery will have a significant impact on our understanding of the structure-function relationships of the YchF subfamily of G proteins in all kingdoms of life.G TP-binding proteins (G proteins) play important roles in diverse fundamental biological processes in living organisms, including signal transduction, cell division, development, intracellular transport, translation, and others (1, 2). The functions and working mechanisms of some ancestral G proteins, which are believed to play essential roles in cellular processes, are still unknown. One such group is the Obg family, which features an N-terminal glycine-rich sequence, followed by a G domain for nucleotide binding and a C-terminal TGS (ThrRS, GTPase, and SpoT) domain that has nucleic acid binding affinity (3).A unique subgroup within the Obg family, the YchF proteins, exhibit relaxed nucleotide-binding specificities (4-6). All G proteins contain a G domain (composed of the G1-G5 motifs) for GTP binding and hydrolysis (4). The G4 motif (canonical sequence: NKxD) confers the specificity for binding GTP (4). In YchFs, the noncanonical G4 sequence (NxxE) is correlated with the loss of nucleotide-binding specificities (4, 5). In some cases, ATP is the preferred ligand (4, 5). However, the physiological significance of the ancient and evolutionarily conserved YchF proteins having the relaxed binding specificities for both ATP and GTP is still unknown.Only a few reports touch on the biological functions of YchF proteins and most focus on human and microorganisms (7-9). The YchF proteins may play a role in iron utilization and regulation of the Ton system in Brucella melitensis (7), and in the growth of the procyclic forms of Trypanosoma cruzi (5). The human YchF homolog hOLA...

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Section: Resultsmentioning

confidence: 43%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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ATP binding by the P-loop NTPase OsYchF1 (an unconventional G protein) contributes to biotic but not abiotic stress responses

Cheung

Miao

et al. 2016

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

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“…This was validated by the observation that hOla1 interacts with BRCA1 (breast cancer-associated gene 1) at the centrosome and that depletion of hOla1 induced centrosome fragmentation (29). Other functions of Ola1/YchF include a possible role in iron uptake in pathogens (8,15) and salinity stress in plants (9,10).…”

Section: Innovationmentioning

confidence: 85%

Redox Activation of the Universally Conserved ATPase YchF by Thioredoxin 1

Hannemann

Suppanz

et al. 2016

Antioxidants & Redox Signaling

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Aims: YchF/Ola1 are unconventional members of the universally conserved GTPase family because they preferentially hydrolyze ATP rather than GTP. These ATPases have been associated with various cellular processes and pathologies, including DNA repair, tumorigenesis, and apoptosis. In particular, a possible role in regulating the oxidative stress response has been suggested for both bacterial and human YchF/Ola1. In this study, we analyzed how YchF responds to oxidative stress and how it potentially regulates the antioxidant response. Results: Our data identify a redox-regulated monomer-dimer equilibrium of YchF as a key event in the functional cycle of YchF. Upon oxidative stress, the oxidation of a conserved and surface-exposed cysteine residue promotes YchF dimerization, which is accompanied by inhibition of the ATPase activity. No dimers were observed in a YchF mutant lacking this cysteine. In vitro, the YchF dimer is dissociated by thioredoxin 1 (TrxA) and this stimulates the ATPase activity. The physiological significance of the YchF-thioredoxin 1 interaction was demonstrated by in vivo cross-linking, which validated this interaction in living cells. This approach also revealed that both the ATPase domain and the helical domain of YchF are in contact with TrxA. Innovation: YchF/Ola1 are the first redox-regulated members of the universally conserved GTPase family and are inactivated by oxidation of a conserved cysteine residue within the nucleotide-binding motif. Conclusion: Our data provide novel insights into the regulation of the so far ill-defined YchF/Ola1 family of proteins and stipulate their role as negative regulators of the oxidative stress response. Antioxid. Redox Signal. 24, 141-156.

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