Group II chaperonins: new TRiC(k)s and turns of a protein folding machine.
In the past decade, the eubacterial group I chaperonin GroEL became the paradigm of a protein folding machine. More recently, electron microscopy and X-ray crystallography offered insights into the structure of the thermosome, the archetype of the group II chaperonins which also comprise the chaperonin from the eukaryotic cytosol TRiC. Some structural differences from GroEL were revealed, namely the existence of a built-in lid provided by the helical protrusions of the apical domains instead of a GroES-like co-chaperonin. These structural studies provide a framework for understanding the differences in the mode of action between the group II and the group I chaperonins. In vitro analyses of the folding of non-native substrates coupled to ATP binding and hydrolysis are progressing towards establishing a functional cycle for group II chaperonins. A protein complex called GimC/prefoldin has recently been found to cooperate with TRiC in vivo, and its characterization is under way.
Gutsche
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Max-Planck-Institute for Biochemistry, Am Klopferspitz 18a, D-82152, Germany.
Essen
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Baumeister
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000494:Allosteric Regulation; D019843:Archaeal Proteins; D018833:Chaperonins / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D006868:Hydrolysis; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D013329:Structure-Activity Relationship; D056405:Thermosomes; D044767:Ubiquitin-Protein Ligases; D056427:t-Complex Genome Region
D019843:Archaeal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D000255:Adenosine Triphosphate; C116196:PPP1R11 protein, human; D044767:Ubiquitin-Protein Ligases; D018833:Chaperonins; D056405:Thermosomes