Cryo-EM reveals an asymmetry in a novel single-ring viral chaperonin

Publication date: Available online 21 December 2019Source: Journal of Structural BiologyAuthor(s): Tatiana B. Stanishneva-Konovalova, Pavel I. Semenyuk, Lidia P. Kurochkina, Evgeny B. Pichkur, Alexander L. Vasilyev, Mikhail V. Kovalchuk, Mikhail P. Kirpichnikov, Olga S. SokolovaAbstractChaperonins are ubiquitously present protein complexes, which assist the proper folding of newly synthesized proteins and prevent aggregation of denatured proteins in an ATP-dependent manner. They are classified into group I (bacterial, mitochondrial, chloroplast chaperonins) and group II (archaeal and eukaryotic cytosolic variants). However, both of these groups do not include recently discovered viral chaperonins. Here, we solved the symmetry-free cryo-EM structures of a single-ring chaperonin encoded by the gene 246 of bacteriophage OBP Pseudomonas fluorescens, in the nucleotide-free, ATPγS-, and ADP-bound states, with a resolution of 4.3Å, 5.0Å, and 6Å, respectively. The structure of OBP chaperonin reveals a unique subunit arrangement, with three subunits pairs and one unpaired subunit. Each pair combines subunits in two possible conformations, differing in nucleotide-binding affinity. Binding of nucleotides result in the increase of subunits’ conformational variability. Due to its unique structural and functional features, OBP chaperonin can represent a new group.148 wordsGraphical abstract

Source: Journal of Structural Biology - December 21, 2019 Category: Biology Source Type: research