Purified chaperonin 60 (groEL) interacts with the nonnative states of a multitude of Escherichia coli proteins.
In vitro experiments employing the soluble proteins from Escherichia coli reveal that about half of them, in their unfolded or partially folded states, but not in their native states, can form stable binary complexes with chaperonin 60 (groEL). These complexes can be isolated by gel filtration chromatography and are efficiently discharged upon the addition of Mg.ATP. Binary complex formation is substantially reduced if chaperonin 60 is presaturated with Rubisco-I, the folding intermediate of Rubisco, but not with native Rubisco. Binary complex formation is also reduced if the transient species that interact with chaperonin 60 are permitted to progress to more stable states. This implies that the structural elements or motifs that are recognized by chaperonin 60 and that are responsible for binary complex formation are only present or accessible in the unfolded states of proteins or in certain intermediates along their respective folding pathways. Given the high-affinity binding that we have observed in the present study and the normal cellular abundance of chaperonin 60, we suspect that the folding of most proteins in E. coli does not occur in free solution spontaneously, but instead takes place while they are associated with molecular chaperones.
Central Research and Development Department, E.I. Du Pont de Nemours & Co. Experimental Station, Wilmington, Delaware 19880-0402.
P V
PV
Viitanen
A A
AA
Gatenby
G H
GH
Lorimer
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D018834:Chaperonin 60; D004926:Escherichia coli / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D017510:Protein Folding; D012247:Rhodospirillum rubrum / Q000201:enzymology; D012273:Ribulose-Bisphosphate Carboxylase / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D013462:Sulfur Radioisotopes
D001426:Bacterial Proteins; D018834:Chaperonin 60; D006360:Heat-Shock Proteins; D013462:Sulfur Radioisotopes; D008715:Methionine; D012273:Ribulose-Bisphosphate Carboxylase