Cryo-EM Structure of the Novel Viral Chaperonin, Encoded by Gene 228 of Bacteriophage AR9 Bacillus subtilis

Chaperonins are some of the most studied families of chaperones. They are multimeric complexes that ensure the proper folding of newly synthesized polypeptide chains and prevent the aggregation of denatured stressed proteins in an ATP-dependent manner. Chaperonins are divided into two groups: group I, found in eubacteria and in endosymbiotic organelles, and group II, found in archaea and the cytosol of eukaryotes [1]. Recently, we demonstrated that some viruses of bacteria (bacteriophages) also encode GroEL-like proteins, which possess chaperonin properties [2–4]. With the addition of new annotated bacteriophage genomes to the database [4,5], the number of predicted GroEL-like proteins has increased. An analysis of their structural and functional characteristics may provide important insights into the diversity of phage chaperonins.