Аннотация:Chaperonins are multimeric protein complexes that assist protein folding in an ATP-dependent way. They were discovered not only in all three kingdoms of life but also in genomes of bacterial viruses (bacteriophages). In contrast to the relatively well-studied bacterial GroEL/GroES complex, phage chaperonins are just beginning to be explored. In this chapter, we summarize the current knowledge of the structures of bacterial and phage chaperonins and discuss the similarities and differences among members of the growing family of chaperonins.