A subcategory of chaperonins found in MITOCHONDRIA; CHLOROPLASTS; and BACTERIA. Group I chaperonins form into a barrel-shaped macromolecular structure that is enclosed by a separate lid-like protein component.

Synonyms: Group I Chaperonins, Type I Chaperonins, Chaperonins, Group I, Chaperonins, Type I, EC 3.6.1.-