9rwq | pdb_00009rwq

Ancestral Group III Chaperonin (ACIII) Double-Ring in Open Conformation including the Equatorial and Intermediate Domains (residues 12-200 and 356-507)

spinqualitylabelsall models 9rwq, resolution 3.21Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9rwq is a 16 chain structure with sequence from Synthetic construct. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 3.21Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Chaperonins are essential protein-folding machines, classified into three structural and phylogenetic groups: Group I (bacterial GroEL), Group II (archaeal thermosome and eukaryotic CCT), and Group III (bacterial thermosome-like). Using ancestral sequence reconstruction (ASR) and protein resurrection, we inferred and experimentally characterized the last common ancestors of these groups (Ancestral Chaperonins ACI, ACII, and ACIII). The resurrected proteins exhibited ATPase activity (except ACII) and protected client proteins from heat-induced inactivation. Structural analyses by electron microscopy and Cryo-EM revealed that ACI forms single 7-mer rings, whereas ACII adopts a mixed population of single/double 8-mer rings, representing the first experimental observation of intermediate oligomeric states. ACII also features a unique cochaperonin-independent closure mechanism, distinct from modern Group I and II chaperonins. Together, these findings provide the experimental structural reconstruction of the most ancient and complex multimeric proteins so far, uncover novel intermediate states in chaperonin evolution, and offer a direct empirical framework for studying the emergence of multimeric complexity in early cellular life. Ancestral Chaperonins Provide the First Structural Glimpse into Early Multimeric Protein Evolution.,Severino R, Cuellar J, Gutierrez-Seijo J, Maestro-Lopez M, Sanchez-Pulido L, Santiago C, Moreno-Paz M, Valpuesta JM, Parro V Mol Biol Evol. 2025 Nov 28:msaf314. doi: 10.1093/molbev/msaf314. PMID:41310978 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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