Structural dynamics of Giα protein revealed by single molecule FRET. 2017

Yongping Zhu, and Lei Zhang, and Xuejun C Zhang, and Yongfang Zhao
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China.

The heterotrimeric G proteins (Gαβγ) act as molecular switches to mediate signal transduction from G protein-coupled receptors to downstream effectors. Upon interaction with an activated receptor, G protein exchanges its bound GDP with GTP, stimulating downstream signal transmission. Release of GDP requires a structural rearrangement between the GTPase domain and helical domain of the Gα subunit. Here, we used single molecule fluorescence resonance energy transfer (smFRET) technique to study the conformational dynamics of these two domains in the apo state and in the binding of different ligands. Direct imaging of individual molecules showed that the Giα subunit is highly dynamic, and at least three major conformations of Giα could be observed in the apo state. Upon binding of GDP, Giα becomes dramatically less dynamic, resulting in a closed conformation between the two domains. We postulate that changes between the three conformations are sequential, and the three conformations appear to have distinct affinities toward GDP.

UI MeSH Term Description Entries
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D011487 Protein Conformation The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain). Conformation, Protein,Conformations, Protein,Protein Conformations
D004789 Enzyme Activation Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D006153 Guanosine Diphosphate A guanine nucleotide containing two phosphate groups esterified to the sugar moiety. GDP,Guanosine 5'-Diphosphate,Guanosine 5'-Trihydrogen Diphosphate,5'-Diphosphate, Guanosine,5'-Trihydrogen Diphosphate, Guanosine,Diphosphate, Guanosine,Diphosphate, Guanosine 5'-Trihydrogen,Guanosine 5' Diphosphate,Guanosine 5' Trihydrogen Diphosphate
D000072417 Protein Domains Discrete protein structural units that may fold independently of the rest of the protein and have their own functions. Peptide Domain,Protein Domain,Domain, Peptide,Domain, Protein,Domains, Peptide,Domains, Protein,Peptide Domains
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D057054 Molecular Imaging The use of molecularly targeted imaging probes to localize and/or monitor biochemical and cellular processes via various imaging modalities that include RADIONUCLIDE IMAGING; ULTRASONOGRAPHY; MAGNETIC RESONANCE IMAGING; FLUORESCENCE IMAGING; and MICROSCOPY. Imaging, Molecular
D019206 GTP-Binding Protein alpha Subunits, Gi-Go A family of heterotrimeric GTP-binding protein alpha subunits that were originally identified by their ability to inhibit ADENYLYL CYCLASES. Members of this family can couple to beta and gamma G-protein subunits that activate POTASSIUM CHANNELS. The Gi-Go part of the name is also spelled Gi/Go. G-Protein, Gi-Go alpha Family,G-Protein, Inhibitory Gi,Gi, Inhibitory G-Protein,G Protein Go,G Protein Subunit alphaoA,G Protein Subunit alphaoC,G(o) Protein,G(o1)alpha,G-Protein, Gi Subunit,G-Protein, Gi-Go Subunits,G-Protein, Go Subunit,G-Protein, Go1 Subunit,G-Protein, Inhibitory Go,GTP-Binding Protein alpha Subunit, Gi,GTP-Binding Protein alpha Subunit, Go,GTP-Binding Protein alpha Subunit, Go1,GTP-Binding Protein alpha Subunit, GoA,GTP-Binding Protein alpha Subunit, GoC,Gi alpha Subunit,Gi-Alpha Protein,Gi-Go G-Proteins,Go Alpha Subunit,Guanine Nucleotide-Binding Protein Go,Ni Protein,Alpha Subunit, Go,G Protein, Gi Go Subunits,G Protein, Gi Go alpha Family,G Protein, Gi Subunit,G Protein, Go Subunit,G Protein, Go1 Subunit,G Protein, Inhibitory Gi,G Protein, Inhibitory Go,G-Proteins, Gi-Go,GTP Binding Protein alpha Subunit, Gi,GTP Binding Protein alpha Subunit, Go,GTP Binding Protein alpha Subunit, Go1,GTP Binding Protein alpha Subunit, GoA,GTP Binding Protein alpha Subunit, GoC,GTP Binding Protein alpha Subunits, Gi Go,Gi Alpha Protein,Gi G-Protein, Inhibitory,Gi Go G Proteins,Gi Subunit G-Protein,Gi, Inhibitory G Protein,Gi-Go Subunits G-Protein,Go G-Protein, Inhibitory,Go Subunit G-Protein,Go, G Protein,Go1 Subunit G-Protein,Guanine Nucleotide Binding Protein Go,Inhibitory G-Protein Gi,Inhibitory Gi G-Protein,Inhibitory Go G-Protein,Subunit G-Protein, Gi,Subunit G-Protein, Go,Subunit G-Protein, Go1,Subunit, Gi alpha,Subunit, Go Alpha,Subunits G-Protein, Gi-Go,alpha Subunit, Gi
D021122 Protein Subunits Single chains of amino acids that are the units of multimeric PROTEINS. Multimeric proteins can be composed of identical or non-identical subunits. One or more monomeric subunits may compose a protomer which itself is a subunit structure of a larger assembly. Protomers,Protein Subunit,Protomer,Subunit, Protein,Subunits, Protein
D031541 Fluorescence Resonance Energy Transfer A type of FLUORESCENCE SPECTROSCOPY using two FLUORESCENT DYES with overlapping emission and absorption spectra, which is used to indicate proximity of labeled molecules. This technique is useful for studying interactions of molecules and PROTEIN FOLDING. Forster Resonance Energy Transfer

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