Together with the chaperonin GroEL, plays an essential role in assisting protein folding (PubMed:2897629, PubMed:2573517, PubMed:10532860, PubMed:1676490, PubMed:16751100, PubMed:18418386, PubMed:18987317, PubMed:20603018, PubMed:24816391). The GroEL-GroES system forms a nano-cage that allows encapsulation of the non-native substrate proteins and provides a physical environment optimized to promote and accelerate protein folding, probably by preventing aggregation and by entropically destabilizing folding intermediates (PubMed:16751100, PubMed:18418386, PubMed:18987317, PubMed:20603018, PubMed:24816391). GroES binds to the apical surface of the GroEL ring, thereby capping the opening of the GroEL channel (PubMed:9285585). Regulates the ATPase activity of GroEL (PubMed:1676490, PubMed:1361169). (Microbial infection) Essential for the assembly of several bacteriophages. Activity of the GroEL-GroES chaperonin complex requires Mg-ATP. Heptamer of 7 subunits arranged in a ring (PubMed:1361169, PubMed:9285585). Interacts with the chaperonin GroEL (PubMed:1361169, PubMed:7638600, PubMed:7638601, PubMed:8618836, PubMed:8663256, PubMed:9285585, PubMed:25174333). Can form asymmetrical complexes, composed of one GroEL and one GroES, and symmetrical complexes, formed between one GroEL and two GroES oligomers (PubMed:1361169, PubMed:7638600, PubMed:7638601, PubMed:8618836, PubMed:8663256, PubMed:25174333). The asymmetrical complex is the functional unit (PubMed:7638600, PubMed:7638601, PubMed:25912285). It was suggested that the symmetric heterooligomer may represent a transient intermediate in the chaperonin protein folding cycle (PubMed:8618836, PubMed:8663256). Another study shows that the symmetric heterooligomers are substantially populated only in the presence of proteins that cannot be folded by the chaperonin (PubMed:25912285). Exclusively localized in foci, usually near 1 cell pole in mid-to-late exponential phase; polar localization depends on the minCDE operon. Foci form near midcell. Belongs to the GroES chaperonin family.