Crystal structure of the open conformation of the mammalian chaperonin CCT in complex with tubulin

• Published in: Nature structural & molecular biology Vol. 18; no. 1; pp. 14 - 19
• Main Authors: Valpuesta, José M, Montoya, Guillermo, Muñoz, Inés G, Yébenes, Hugo, Zhou, Min, Mesa, Pablo, Serna, Marina, Park, Ah Young, Bragado-Nilsson, Elisabeth, Beloso, Ana, de Cárcer, Guillermo, Malumbres, Marcos, Robinson, Carol V
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.01.2011; Nature Publishing Group
• Subjects: 631/45/535; 631/57/2272/2273; Animals; ATP; Binding Sites; Biochemistry; Biological Microscopy; Biomedical and Life Sciences; Cattle; Chaperonin Containing TCP-1 - chemistry; Crystal structure; Crystallography, X-Ray; Life Sciences; Mass Spectrometry; Membrane Biology; Models, Molecular; Molecular biology; Molecular chaperones; Physiological aspects; Protein Folding; Protein Structure; Protein Structure, Tertiary; Protein Subunits - chemistry; Structure; Substrates; Tubulin - chemistry; Tubulin - metabolism; Tubulins; United Kingdom; Spain
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.1971

CCT/TRiC is a eukaryotic multi-subunit chaperonin that promotes the correct folding of many cytosolic proteins, including tubulin, within its cavity. Now the crystal structure of CCT in its open state is solved to 5.5-Å resolution and, together with EM and biochemical analysis, allows the observation of a bound tubulin molecule interacting with CCT loops in the apical and equatorial domains. Protein folding is assisted by molecular chaperones. CCT (chaperonin containing TCP-1, or TRiC) is a 1-MDa oligomer that is built by two rings comprising eight different 60-kDa subunits. This chaperonin regulates the folding of important proteins including actin, α-tubulin and β-tubulin. We used an electron density map at 5.5 Å resolution to reconstruct CCT, which showed a substrate in the inner cavities of both rings. Here we present the crystal structure of the open conformation of this nanomachine in complex with tubulin, providing information about the mechanism by which it aids tubulin folding. The structure showed that the substrate interacts with loops in the apical and equatorial domains of CCT. The organization of the ATP-binding pockets suggests that the substrate is stretched inside the cavity. Our data provide the basis for understanding the function of this chaperonin.