title: Structures of the Gβ-CCT and PhLP1-Gβ-CCT complexes reveal a mechanism for G-protein β-subunit folding and Gβγ dimer assembly.
abstract: G-protein signaling depends on the ability of the individual subunits of the G-protein heterotrimer to assemble into a functional complex. Formation of the G-protein βγ (Gβγ) dimer is particularly challenging because it is an obligate dimer in which the individual subunits are unstable on their own. Recent studies have revealed an intricate chaperone system that brings Gβ and Gγ together. This system includes cytosolic chaperonin containing TCP-1 (CCT; also called TRiC) and its cochaperone phosducin-like protein 1 (PhLP1). Two key intermediates in the Gβγ assembly process, the Gβ-CCT and the PhLP1-Gβ-CCT complexes, were isolated and analyzed by a hybrid structural approach using cryo-electron microscopy, chemical cross-linking coupled with mass spectrometry, and unnatural amino acid cross-linking. The structures show that Gβ interacts with CCT in a near-native state through interactions of the Gγ-binding region of Gβ with the CCTγ subunit. PhLP1 binding stabilizes the Gβ fold, disrupting interactions with CCT and releasing a PhLP1-Gβ dimer for assembly with Gγ. This view provides unique insight into the interplay between CCT and a cochaperone to orchestrate the folding of a protein substrate.
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602;
authors: Rebecca L
authors: RL
authors: Plimpton
authors: Centro Nacional de Biotecnología, Campus de la Universidad Autónoma de Madrid, 28049 Madrid, Spain; and.
authors: Jorge
authors: J
authors: Cuéllar
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602;
authors: Chun Wan J
authors: CW
authors: Lai
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602;
authors: Takuma
authors: T
authors: Aoba
authors: Department of Internal Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112.
authors: Aman
authors: A
authors: Makaju
authors: Department of Internal Medicine, Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112.
authors: Sarah
authors: S
authors: Franklin
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602;
authors: Andrew D
authors: AD
authors: Mathis
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602;
authors: John T
authors: JT
authors: Prince
authors: Centro Nacional de Biotecnología, Campus de la Universidad Autónoma de Madrid, 28049 Madrid, Spain; and.
authors: José L
authors: JL
authors: Carrascosa
authors: Centro Nacional de Biotecnología, Campus de la Universidad Autónoma de Madrid, 28049 Madrid, Spain; and bmwillardson@chem.byu.edu jmv@cnb.csic.es.
authors: José M
authors: JM
authors: Valpuesta
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602; bmwillardson@chem.byu.edu jmv@cnb.csic.es.
authors: Barry M
authors: BM
authors: Willardson
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001577:Benzophenones; D002352:Carrier Proteins / Q000737:chemistry* / Q000648:ultrastructure; D056404:Chaperonin Containing TCP-1 / Q000737:chemistry* / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000378:metabolism; D020285:Cryoelectron Microscopy; D044387:GTP-Binding Protein beta Subunits / Q000737:chemistry* / Q000648:ultrastructure; D044388:GTP-Binding Protein gamma Subunits / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D013058:Mass Spectrometry; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000648:ultrastructure; D010649:Phenylalanine / Q000031:analogs & derivatives; D055503:Protein Multimerization; D017433:Protein Structure, Secondary
chemical_list: C488060:4-benzoylphenylalanine; D000596:Amino Acids; D001577:Benzophenones; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D009419:Nerve Tissue Proteins; C098789:PDCL protein, human; D010649:Phenylalanine; D056404:Chaperonin Containing TCP-1
keywords: G-protein; chaperonin; cross-linking; electron cryo-microscopy; phosducin-like protein