Structural and mechanistic characterization of an archaeal-like chaperonin from a thermophilic bacterium

• Published in: Nature communications Vol. 8; no. 1; pp. 827 - 11
• Main Authors: An, Young Jun, Rowland, Sara E., Na, Jung-Hyun, Spigolon, Dario, Hong, Seung Kon, Yoon, Yeo Joon, Lee, Jung-Hyun, Robb, Frank T., Cha, Sun-Shin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10.10.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 631/45/535/1266/1265; 631/92/603; Adenosine triphosphate; Allosteric properties; Bacteria; Chambers; Chaperonins; Crystal structure; Folding machines; Humanities and Social Sciences; multidisciplinary; Phylogeny; Protein folding; Proteins; Science; Science (multidisciplinary); Structural analysis
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-017-00980-z

The chaperonins (CPNs) are megadalton sized hollow complexes with two cavities that open and close to encapsulate non-native proteins. CPNs are assigned to two sequence-related groups that have distinct allosteric mechanisms. In Group I CPNs a detachable co-chaperone, GroES, closes the chambers whereas in Group II a built-in lid closes the chambers. Group I CPNs have a bacterial ancestry, whereas Group II CPNs are archaeal in origin. Here we describe open and closed crystal structures representing a new phylogenetic branch of CPNs. These Group III CPNs are divergent in sequence and structure from extant CPNs, but are closed by a built-in lid like Group II CPNs. A nucleotide-sensing loop, present in both Group I and Group II CPNs, is notably absent. We identified inter-ring pivot joints that articulate during ring closure. These Group III CPNs likely represent a relic from the ancestral CPN that formed distinct bacterial and archaeal branches. Chaperonins (CPNs) are ATP-dependent protein-folding machines. Here the authors present the open and closed crystal structures of a Group III CPN from the thermophilic bacterium Carboxydothermus hydrogenoformans , discuss its mechanism and structurally compare it with Group I and II CPNs.