Publications (107)425.52 Total impact
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Article: Nuclear magnetic resonance approaches for characterizing interactions between the bacterial chaperonin GroEL and unstructured proteins.
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ABSTRACT: GroEL-protein interactions were characterized by stable isotope-assisted nuclear magnetic resonance (NMR) spectroscopy using chemically denatured bovine rhodanese and an intrinsically disordered protein, α-synuclein, as model ligands. NMR data indicated that proteins tethered to GroEL remain largely unfolded and highly mobile, enabling identification of the interaction hot spots displayed on intrinsically disordered proteins.Journal of Bioscience and Bioengineering 04/2013; · 1.79 Impact Factor -
Article: A Gel-Encapsulated Bioreactor System for NMR Studies of Protein-Protein Interactions in Living Mammalian Cells.
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ABSTRACT: Staying alive: The major limitation of in-cell NMR methods is the occurrence of cell death during the NMR measurement. To overcome this problem, a bioreactor was utilized that can perfuse the cells in the NMR tube, thereby maintaining the conditions for greater than 5 h. By using the bioreactor, the binding site of an externally introduced protein for an endogenous molecule in HeLa S3 cells was identified.Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor -
Article: Structural Basis of Efficient Electron Transport between Photosynthetic Membrane Proteins and Plastocyanin in Spinach Revealed Using Nuclear Magnetic Resonance.
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ABSTRACT: In the photosynthetic light reactions of plants and cyanobacteria, plastocyanin (Pc) plays a crucial role as an electron carrier and shuttle protein between two membrane protein complexes: cytochrome b(6)f (cyt b(6)f) and photosystem I (PSI). The rapid turnover of Pc between cyt b(6)f and PSI enables the efficient use of light energy. In the Pc-cyt b(6)f and Pc-PSI electron transfer complexes, the electron transfer reactions are accomplished within <10(-4) s. However, the mechanisms enabling the rapid association and dissociation of Pc are still unclear because of the lack of an appropriate method to study huge complexes with short lifetimes. Here, using the transferred cross-saturation method, we investigated the residues of spinach (Spinacia oleracea) Pc in close proximity to spinach PSI and cyt b(6)f, in both the thylakoid vesicle-embedded and solubilized states. We demonstrated that the hydrophobic patch residues of Pc are in close proximity to PSI and cyt b(6)f, whereas the acidic patch residues of Pc do not form stable salt bridges with either PSI or cyt b(6)f, in the electron transfer complexes. The transient characteristics of the interactions on the acidic patch facilitate the rapid association and dissociation of Pc.The Plant Cell 10/2012; · 8.99 Impact Factor -
Article: Functional Equilibrium of the KcsA Structure Revealed by NMR.
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ABSTRACT: KcsA is a tetrameric K(+) channel that is activated by acidic pH. Under open conditions of the helix bundle crossing, the selectivity filter undergoes an equilibrium between permeable and impermeable conformations. Here, we report that population of the permeable conformation (p(perm)) positively correlates with the tetrameric stability and that the population in reconstituted high density lipoprotein (rHDL), where KcsA is surrounded by the lipid bilayer, is lower than that in detergent micelles, indicating that dynamic properties of KcsA are different in these two media. Perturbation of the membrane environment by the addition of 1-3% 2,2,2-trifluoroethanol (TFE) increases p(perm) and the open probability, revealed by NMR and single channel recording analyses. These results demonstrate that KcsA inactivation is determined not only by the protein itself, but also by the surrounding membrane environments.Journal of Biological Chemistry 09/2012; · 4.77 Impact Factor -
Article: Biological role of the two overlapping poly(A)-binding protein interacting motifs 2 (PAM2) of eukaryotic releasing factor eRF3 in mRNA decay.
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ABSTRACT: Eukaryotic releasing factor GSPT/eRF3 mediates translation termination-coupled mRNA decay via interaction with a cytosolic poly(A)-binding protein (PABPC1). A region of eRF3 containing two overlapping PAM2 (PABPC1-interacting motif 2) motifs is assumed to bind to the PABC domain of PABPC1, on the poly(A) tail of mRNA. PAM2 motifs are also found in the major deadenylases Caf1-Ccr4 and Pan2-Pan3, whose activities are enhanced upon PABPC1 binding to these motifs. Their deadenylase activities are regulated by eRF3, in which two overlapping PAM2 motifs competitively prevent interaction with PABPC1. However, it is unclear how these overlapping motifs recognize PABC and regulate deadenylase activity in a translation termination-coupled manner. We used a dominant-negative approach to demonstrate that the N-terminal PAM2 motif is critical for eRF3 binding to PABPC1 and that both motifs are required for function. Isothermal titration calorimetry (ITC) and NMR analyses revealed that the interaction is in equilibrium between the two PAM2-PABC complexes, where only one of the two overlapping PAM2 motifs is PABC-bound and the other is PABC-unbound and partially accessible to the other PABC. Based on these results, we proposed a biological role for the overlapping PAM2 motifs in the regulation of deadenylase accessibility to PABPC1 at the 3' end of poly(A).RNA 09/2012; 18(11):1957-67. · 5.09 Impact Factor -
Article: Efficacy of the β(2)-adrenergic receptor is determined by conformational equilibrium in the transmembrane region.
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ABSTRACT: Many drugs that target G-protein-coupled receptors (GPCRs) induce or inhibit their signal transduction with different strengths, which affect their therapeutic properties. However, the mechanism underlying the differences in the signalling levels is still not clear, although several structures of GPCRs complexed with ligands determined by X-ray crystallography are available. Here we utilized NMR to monitor the signals from the methionine residue at position 82 in neutral antagonist- and partial agonist-bound states of β(2)-adrenergic receptor (β(2)AR), which are correlated with the conformational changes of the transmembrane regions upon activation. We show that this residue exists in a conformational equilibrium between the inverse agonist-bound states and the full agonist-bound state, and the population of the latter reflects the signal transduction level in each ligand-bound state. These findings provide insights into the multi-level signalling of β(2)AR and other GPCRs, including the basal activity, and the mechanism of signal transduction mediated by GPCRs.Nature Communications 09/2012; 3:1045. · 7.40 Impact Factor -
Article: Structural Basis for the Golgi Association by the Pleckstrin Homology Domain of the Ceramide Trafficking Protein (CERT).
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ABSTRACT: Ceramide transport from the endoplasmic reticulum to the Golgi apparatus is crucial in sphingolipid biosynthesis, and the process relies on the ceramide trafficking protein (CERT), which contains pleckstrin homology (PH) and StAR-related lipid transfer domains. The CERT PH domain specifically recognizes phosphatidylinositol 4-monophosphate (PtdIns(4)P), a characteristic phosphoinositide in the Golgi membrane, and is indispensable for the endoplasmic reticulum-to-Golgi transport of ceramide by CERT. In this study, we determined the three-dimensional structure of the CERT PH domain by using solution NMR techniques. The structure revealed the presence of a characteristic basic groove near the canonical PtdIns(4)P recognition site. An extensive interaction study using NMR and other biophysical techniques revealed that the basic groove coordinates the CERT PH domain for efficient PtdIns(4)P recognition and localization in the Golgi apparatus. The notion was also supported by Golgi mislocalization of the CERT mutants in living cells. The distinctive binding modes reflect the functions of PH domains, as the basic groove is conserved only in the PH domains involved with the PtdIns(4)P-dependent lipid transport activity but not in those with the signal transduction activity.Journal of Biological Chemistry 08/2012; 287(40):33706-18. · 4.77 Impact Factor -
Article: Segmental isotopic labeling of a 140 kDa dimeric multi-domain protein CheA from Escherichia coli by expressed protein ligation and protein trans-splicing.
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ABSTRACT: Segmental isotopic labeling is a powerful labeling tool to facilitate NMR studies of larger proteins by not only alleviating the signal overlap problem but also retaining features of uniform isotopic labeling. Although two approaches, expressed protein ligation (EPL) and protein trans-splicing (PTS), have been mainly used for segmental isotopic labeling, there has been no single example in which both approaches have been directly used with an identical protein. Here we applied both EPL and PTS methods to a 140 kDa dimeric multi-domain protein E. coli CheA, and successfully produced the ligated CheA dimer by both approaches. In EPL approach, extensive optimization of the ligation sites and the conditions were required to obtain sufficient amount for an NMR sample of CheA, because CheA contains a dimer forming domain and it was not possible to achieve high reactant concentrations (1-5 mM) of CheA fragments for the ideal EPL condition, thereby resulting in the low yield of segmentally labelled CheA dimer. PTS approach sufficiently produced segmentally labeled ligated CheA in vivo as well as in vitro without extensive optimizations. This is presumably because CheA has self-contained domains connected with long linkers, accommodating a seven-residue mutation without loss of the function, which was introduced by PTS to achieve the high yield. PTS approach was less laborious than EPL approach for the routine preparation of segmentally-isotope labeled CheA dimer. Both approaches remain to be further developed for facilitating preparations of segmental isotope-labelled samples without extensive optimizations for ligation.Journal of Biomolecular NMR 06/2012; 53(3):191-207. · 3.61 Impact Factor -
Article: Spatial distribution of cytoplasmic domains of the Mg(2+)-transporter MgtE, in a solution lacking Mg(2+), revealed by paramagnetic relaxation enhancement.
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ABSTRACT: MgtE is a prokaryotic Mg(2+) transporter that controls cellular Mg(2+) concentrations. We previously reported crystal structures of the cytoplasmic region of MgtE, consisting of 2 domains, that is, N and CBS, in the Mg(2+)-free and Mg(2+)-bound forms. The Mg(2+)-binding sites lay at the interface of the 2 domains, making the Mg(2+)-bound form compact and globular. In the Mg(2+)-free structure, however, the domains are far apart, and the Mg(2+)-binding sites are destroyed. Therefore, it is unclear how Mg(2+)-free MgtE changes its conformation to accommodate Mg(2+) ions. Here, we used paramagnetic relaxation enhancement (PRE) to characterize the relative orientation of the N and CBS domains in the absence of Mg(2+) in solution. When the residues on the surface of the CBS domain were labeled with nitroxide tags, significant PRE effects were observed for the residues in the N domain. No single structure satisfied the PRE profiles, suggesting that the N and CBS domains are not fixed in a particular orientation in solution. We then conducted ensemble simulated annealing calculations in order to obtain the atomic probability density and visualize the spatial distribution of the N domain in solution. The results indicate that the N domain tends to occupy the space near its position in the Mg(2+)-bound crystal structure, facilitating efficient capture of Mg(2+) with increased intracellular Mg(2+) concentration, which is necessary to close the gate.Biochimica et Biophysica Acta 06/2012; 1824(10):1129-35. · 4.66 Impact Factor -
Article: Structural basis for modulation of gating property of G protein-gated inwardly rectifying potassium ion channel (GIRK) by i/o-family G protein α subunit (Gαi/o).
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ABSTRACT: G protein-gated inwardly rectifying potassium channel (GIRK) plays a crucial role in regulating heart rate and neuronal excitability. The gating of GIRK is regulated by the association and dissociation of G protein βγ subunits (Gβγ), which are released from pertussis toxin-sensitive G protein α subunit (Gα(i/o)) upon GPCR activation in vivo. Several lines of evidence indicate that Gα(i/o) also interacts directly with GIRK, playing functional roles in the signaling efficiency and the modulation of the channel activity. However, the underlying mechanism for GIRK regulation by Gα(i/o) remains to be elucidated. Here, we performed NMR analyses of the interaction between the cytoplasmic region of GIRK1 and Gα(i3) in the GTP-bound state. The NMR spectral changes of Gα upon the addition of GIRK as well as the transferred cross-saturation (TCS) results indicated their direct binding mode, where the K(d) value was estimated as ∼1 mm. The TCS experiments identified the direct binding sites on Gα and GIRK as the α2/α3 helices on the GTPase domain of Gα and the αA helix of GIRK. In addition, the TCS and paramagnetic relaxation enhancement results suggested that the helical domain of Gα transiently interacts with the αA helix of GIRK. Based on these results, we built a docking model of Gα and GIRK, suggesting the molecular basis for efficient GIRK deactivation by Gα(i/o).Journal of Biological Chemistry 04/2012; 287(23):19537-49. · 4.77 Impact Factor -
Article: Backbone resonance assignments for the cytoplasmic region of the Mg(2+) transporter MgtE in the Mg (2+)-unbound state.
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ABSTRACT: Magnesium ion (Mg(2+)) is an essential metal element for life, and has many cellular functions, including ATP utilization, activation of enzymes, and maintenance of genomic stability. The intracellular Mg(2+) concentration is regulated by a class of transmembrane proteins, called Mg(2+) transporters. One of the prokaryotic Mg(2+) transporters, MgtE, is a 450-residue protein, and functions as a dimer. We previously reported that MgtE exhibits the channel-like electrophysiological property, i.e., it permeates Mg(2+) according to the electrochemical potential of Mg(2+). The Mg(2+)-permeation pathway opens in response to the decrease of the intracellular Mg(2+) concentration, while it is completely closed at the intracellular Mg(2+) concentration of 10 mM. The crystal structures of the MgtE dimer revealed that the Mg(2+)-sensing cytoplasmic region consists of the N and CBS domains. The Mg(2+)-bound state of MgtE adopts a compact, globular conformation, which is stabilized by the coordination of a number of Mg(2+) ions between these domains. On the other hand, in the Mg(2+)-unbound state, these domains are far apart, and fixed by the crystal packing. Therefore, structural analyses in solution were awaited, in order to characterize the Mg(2+)-dependent alteration of the MgtE structure and dynamics relevant to its gating. In this paper, we report the backbone resonance assignments of the dimer of the cytoplasmic region of the MgtE from Thermus thermophilus with a molecular weight of 60 KDa, in the Mg(2+)-unbound state.Biomolecular NMR Assignments 04/2012; · 0.72 Impact Factor -
Article: Atypical membrane-embedded phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2)-binding site on p47(phox) Phox homology (PX) domain revealed by NMR.
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ABSTRACT: The Phox homology (PX) domain is a functional module that targets membranes through specific interactions with phosphoinositides. The p47(phox) PX domain preferably binds phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) and plays a pivotal role in the assembly of phagocyte NADPH oxidase. We describe the PI(3,4)P(2) binding mode of the p47(phox) PX domain as identified by a transferred cross-saturation experiment. The identified PI(3,4)P(2)-binding site, which includes the residues of helices α1 and α1' and the following loop up to the distorted left-handed PP(II) helix, is located at a unique position, as compared with the phosphoinositide-binding sites of all other PX domains characterized thus far. Mutational analyses corroborated the results of the transferred cross-saturation experiments. Moreover, experiments with intact cells demonstrated the importance of this unique binding site for the function of the NADPH oxidase. The low affinity and selectivity of the atypical phosphoinositide-binding site on the p47(phox) PX domain suggest that different types of phosphoinositides sequentially bind to the p47(phox) PX domain, allowing the regulation of the multiple events that characterize the assembly and activation of phagocyte NADPH oxidase.Journal of Biological Chemistry 04/2012; 287(21):17848-59. · 4.77 Impact Factor -
Article: Backbone resonance assignments for G protein α(i3) subunit in the GTP-bound state.
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ABSTRACT: Guanine-nucleotide binding proteins (G proteins) act as molecular switches in signaling pathways, by coupling the activation of G protein-coupled receptors (GPCRs) at the cell surface to intracellular responses. In the resting state, G protein forms a heterotrimer, consisting of GDP-bound form of the G protein α subunit (Gα(GDP)) and G protein βγ subunit (Gβγ). Ligand binding to GPCRs promotes the GDP-GTP exchange on Gα, leading to the dissociation of the GTP-bound form of Gα (Gα(GTP)) and Gβγ. Then, Gα(GTP) and Gβγ bind to their downstream effector enzymes or ion channels and regulate their activities, leading to a variety of cellular responses. Finally, Gα hydrolyzes the bound GTP to GDP and returns to the resting state by re-associating with Gβγ. G proteins are classified with four major families based on the amino acid sequences of Gα: i/o, s, q/11, and 12/13. Each family transduces the signaling from different GPCRs to the specific effectors. Here, we established the backbone resonance assignments of human Gα(i3), a member of the i/o family, with a molecular weight of 41 K in complex with a GTP analogue, GTPγS.Biomolecular NMR Assignments 01/2012; 6(2):217-20. · 0.72 Impact Factor -
Article: Isotopic labeling of heterologous proteins in the yeast Pichia pastoris and Kluyveromyces lactis.
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ABSTRACT: Several protein expression systems are available for the preparation of stable isotope-labeled recombinant proteins for NMR studies. Yeast expression systems have several advantages over prokaryotic systems, such as the widely used Escherichia coli expression system. Protein expression using the methylotrophic yeast Pichia pastoris is commonly employed for the preparation of isotope-labeled proteins. Recently, the hemiascomycete yeast Kluyveromyces lactis expression system was reported as being useful for preparing proteins for NMR studies. Since each yeast expression system has different features, their applications have increased in number. In this chapter, we describe procedures for the efficient production of uniformly isotope-labeled proteins using the P. pastoris and the K. lactis yeast expression systems.Methods in molecular biology (Clifton, N.J.) 01/2012; 831:19-36. -
Article: An NMR method to study protein-protein interactions.
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ABSTRACT: Specific interactions between proteins are a fundamental process underlying the various biological events, such as cell-cell contacts, signal transduction, and gene expression. Therefore, the structural investigations of protein-protein interactions provide useful information for understanding these events. We describe an NMR method, termed the cross-saturation (CS) method, to determine the binding sites of protein complexes more precisely than conventional NMR methods. The CS method can determine the binding sites of a protein complex that undergoes fast exchange between the free and the bound states, regardless of the molecular size of the complex.Methods in molecular biology (Clifton, N.J.) 01/2012; 757:129-37. -
Article: An accurate pharmacophore mapping method by NMR spectroscopy.
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ABSTRACT: Irradiation makes the difference: The relaxation-rate differences of individual ligand protons (H(A) , H(B) ) between the experiment with and that without (blue) saturation of the protons of the protein target reflect the proximity to the protein surface. Thus the binding portions of ligand molecules could be identified using this "difference of inversion recovery rate with and without target irradiation" (DIRECTION) methodology.Angewandte Chemie International Edition 12/2011; 51(6):1362-5. · 13.45 Impact Factor -
Article: [Two-state equilibrium of hyaluronan-binding domain is crucial for CD44-mediated cell rolling].
Seikagaku. The Journal of Japanese Biochemical Society 10/2011; 83(10):893-901. · 0.04 Impact Factor -
Article: Affinity transfer to a human protein by CDR3 grafting of camelid VHH.
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ABSTRACT: VHH is the binding domain of the IgG heavy chain. Some VHHs have an extremely long CDR3 that contributes to antigen binding. We studied the antigen binding ability of CDR3 by grafting a CDR3 from an antigen-binding VHH onto a nonbinding VHH. cAb-CA05-(1RI8), the CDR3-grafted VHH, had an antigen-binding ability. To find a human scaffold protein acceptable for VHH CDR3 grafting, we focused on the conserved structure of VHH, especially the N-terminal and C-terminal amino acid residues of the CDR3 loop and the Cys residue of CDR1. Human origin protein structures with the same orientation were searched in PDB and ubiquitin was selected. Ubi-(1RI8), the CDR3-grafted ubiquitin, had antigen-binding ability, though the affinity was relatively low compared to cAb-CA05-(1RI8). The thermodynamic parameters of Ubi-(1RI8) binding to HEWL were different from cAb-CA05-(1RI8). Hydrogen-deuterium exchange experiments showed decreased stability around the CDR3 grafting region of Ubi-(1RI8), which might explain the decreased antigen-binding ability and the differences in thermodynamic properties. We concluded that the orientation of the CDR3 sequence of Ubi-(1RI8) could not be reconstructed correctly.Protein Science 09/2011; 20(12):1971-81. · 2.80 Impact Factor -
Article: Protein-ligand docking guided by ligand pharmacophore-mapping experiment by NMR.
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ABSTRACT: We developed a new protein-ligand docking calculation method using experimental NMR data. Recently, we proposed a novel ligand epitope-mapping experiment, which utilizes the difference between the longitudinal relaxation rates of ligand protons with and without irradiation of target protein protons (DIRECTION epitope-mapping experiment; Y. Mizukoshi, et al., An accurate pharmacophore mapping method by NMR, submitted for publication). Although the epitope-mapping experiment is simple and rapid, the result should reflect the proximity of ligand protons to the target protein surface. However, it cannot directly provide the protein-ligand complex structure without any other structural information. While the accuracy of protein-ligand docking software is insufficient, the software can provide many candidate complex structures. In many cases, the correct complex structure is included in the set of predicted complex structures and the correct structures could be selected by applying the above experimental result of ligand epitope mapping. In the current study, we combined the protein-ligand docking software with the NMR experimental information so as to improve the prediction of the protein-ligand complex structure. Consequently, the prediction accuracy was improved by 1.3-1.9 times (from ca. 50% to ca. 70%) in a self-docking test for the simulated epitope mapping result. Moreover, this method was applied to actual NMR experiments, and it successfully reconstructed the protein-ligand complex structures.Journal of molecular graphics & modelling 09/2011; 31:20-7. · 2.17 Impact Factor -
Article: Rapid identification of protein-protein interfaces for the construction of a complex model based on multiple unassigned signals by using time-sharing NMR measurements.
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ABSTRACT: Protein-protein interactions are necessary for various cellular processes, and therefore, information related to protein-protein interactions and structural information of complexes is invaluable. To identify protein-protein interfaces using NMR, resonance assignments are generally necessary to analyze the data; however, they are time consuming to collect, especially for large proteins. In this paper, we present a rapid, effective, and unbiased approach for the identification of a protein-protein interface without resonance assignments. This approach requires only a single set of 2D titration experiments of a single protein sample, labeled with a unique combination of an (15)N-labeled amino acid and several amino acids (13)C-labeled on specific atoms. To rapidly obtain high resolution data, we applied a new pulse sequence for time-shared NMR measurements that allowed simultaneous detection of a ω(1)-TROSY-type backbone (1)H-(15)N and aromatic (1)H-(13)C shift correlations together with single quantum methyl (1)H-(13)C shift correlations. We developed a structure-based computational approach, that uses our experimental data to search the protein surfaces in an unbiased manner to identify the residues involved in the protein-protein interface. Finally, we demonstrated that the obtained information of the molecular interface could be directly leveraged to support protein-protein docking studies. Such rapid construction of a complex model provides valuable information and enables more efficient biochemical characterization of a protein-protein complex, for instance, as the first step in structure-guided drug development.Journal of Structural Biology 06/2011; 174(3):434-42. · 3.41 Impact Factor
Top co-authors
Top Journals
Institutions
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1992–2012
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The University of Tokyo
- • Faculty & Graduate School of Pharmaceutical Sciences
- • Department of Pharmaceutical Sciences
Tokyo, Tokyo-to, Japan
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2006–2010
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National Institute of Advanced Industrial Science and Technology
- Biomedicinal Information Research Center
Tokyo, Tokyo-to, Japan
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2007–2009
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Dainippon Sumitomo Pharma Co., Ltd.
Ōsaka-shi, Osaka-fu, Japan
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2005
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Keio University
- Department of Physics
Tokyo, Tokyo-to, Japan
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2004
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Meiji Pharmaceutical University
Tokyo, Tokyo-to, Japan
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1998–2000
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Suntory Institute for Bioorganic Research
Ōsaka-shi, Osaka-fu, Japan
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1999
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Nara Institute of Science and Technology
Ikoma, Nara, Japan
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