title: The structural basis of substrate recognition by the eukaryotic chaperonin TRiC/CCT.
abstract: The eukaryotic chaperonin TRiC (also called CCT) is the obligate chaperone for many essential proteins. TRiC is hetero-oligomeric, comprising two stacked rings of eight different subunits each. Subunit diversification from simpler archaeal chaperonins appears linked to proteome expansion. Here, we integrate structural, biophysical, and modeling approaches to identify the hitherto unknown substrate-binding site in TRiC and uncover the basis of substrate recognition. NMR and modeling provided a structural model of a chaperonin-substrate complex. Mutagenesis and crosslinking-mass spectrometry validated the identified substrate-binding interface and demonstrate that TRiC contacts full-length substrates combinatorially in a subunit-specific manner. The binding site of each subunit has a distinct, evolutionarily conserved pattern of polar and hydrophobic residues specifying recognition of discrete substrate motifs. The combinatorial recognition of polypeptides broadens the specificity of TRiC and may direct the topology of bound polypeptides along a productive folding trajectory, contributing to TRiC's unique ability to fold obligate substrates.
authors.affiliation: Department of Biology and Genetics, Stanford University, Stanford, CA 94305, USA. Electronic address: lajoachi@gmail.com.
authors.forename: Lukasz A
authors.initials: LA
authors.lastname: Joachimiak
authors.affiliation: Institute of Molecular Systems Biology, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland; Ph.D. Program in Molecular Life Sciences, University of Zurich/ETH Zurich, 8057 Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Walzthoeni
authors.affiliation: Stanford Magnetic Resonance Laboratory, Stanford University, Stanford, CA 94305, USA.
authors.forename: Corey W
authors.initials: CW
authors.lastname: Liu
authors.affiliation: Institute of Molecular Systems Biology, Department of Biology, ETH Zurich, 8093 Zurich, Switzerland; Faculty of Science, University of Zurich, 8006 Zurich, Switzerland.
authors.forename: Ruedi
authors.initials: R
authors.lastname: Aebersold
authors.affiliation: Department of Biology and Genetics, Stanford University, Stanford, CA 94305, USA. Electronic address: jfrydman@stanford.edu.
authors.forename: Judith
authors.initials: J
authors.lastname: Frydman
mesh_terms: D000818:Animals; D001105:Archaea / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D056404:Chaperonin Containing TCP-1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D056890:Eukaryota / Q000737:chemistry* / Q000166:cytology; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D019843:Archaeal Proteins; D056404:Chaperonin Containing TCP-1