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As a large family of hydrolases,GTPases are widespread in cells and play the very important biological function of hydrolyzing GTP into GDP and inorganic phosphate through binding with it.GTPases are involved in cell cycle regulation,protein synthesis,and protein transportation.Chaperones can facilitate the folding or refolding of nascent peptides and denatured proteins to their native states.However,chaperones do not occur in the native structures in which they can perform their normal biological functions.In the current study,the chaperone activity of the conssrvsd GTPases of Escherichia coli is tested by the chemical denaturation and chaperone-assisted renaturation of citrate synthase and α-glucosidase.The effects of ribosomes and nucleotides on the chaperone activity are also examined.Our data indicate that these conserved GTPases have chaperone properties,and may be ancestral protein folding factors that have appeared before dedicated chaperones.