GroEL Binds Artificial Proteins with Random Sequences

Abstract

Chaperonin GroEL from Escherichia coli binds to the non-native states of many unrelated proteins, and GroEL-recognizable structural features have been argued. As model substrate proteins of GroEL, we used seven artificial proteins (138ϳ141 residues), each of which has a unique but randomly chosen amino acid sequence and no propensity to fold into a certain structure. Two of them were water-soluble, and the rest were soluble in 3 M urea. The soluble ones interacted with GroEL in a manner similar to that of a natural substrate; they stimulated the ATPase cycle of GroEL and GroEL/ GroES and inhibited GroEL-assisted folding of other protein. All seven artificial proteins were able to bind to GroEL. The results suggest that the secondary structure as well as the specific sequence motif of the substrate proteins are not necessary to be recognized by GroEL.

Effect of the C-terminal Truncation on the Functional Cycle of Chaperonin GroEL

“…1, filled bar). As reported previously (27)(28)(29), when substrate proteins such as rLA, denatured pepsin, and denatured rhodanese were present, the rate of ATP hydrolysis was enhanced (Fig. 1, open bar).…”

The Chaperonins of Synechocystis PCC 6803 Differ in Heat Inducibility and Chaperone Activity

“…This is supported by a number of observations: (i) Using artificial proteins with random sequences, Aoki et al (5) demonstrated that neither a specific secondary structure nor a sequence motif of the substrate proteins is necessary for recognition by GroEL. (ii) Ewalt and coworkers (6) found that about 10 -15% of the newborn proteins in E. coli cells are present in a complex with the GroEL oligomer during optimal growth conditions, while 30% are bound by chaperonins during heatstress.…”

Probing Open Conformation of GroEL Rings by Cross-linking Reveals Single and Double Open Ring Structures of GroEL in ADP and ATP

“…GroEL OO Can Hydrolyze ATP but There Is No Stimulation by Substrate Protein-As is well known, ATPase activity of GroEL is suppressed by GroES and stimulated by substrate protein (denatured MDH) (16,22,30) (Fig. 6).…”