Article: article from journal or magazin.
Chaperonin-facilitated refolding of ribulosebisphosphate carboxylase and ATP hydrolysis by chaperonin 60 (groEL) are K+ dependent.
Both the chaperonin- and MgATP-dependent reconstitution of unfolded ribulosebisphosphate carboxylase (Rubisco) and the uncoupled ATPase activity of chaperonin 60 (groEL) require ionic potassium. The spontaneous, chaperonin-independent reconstitution of Rubisco, observed at 15 but not at 25 degrees C, requires no K+ and is actually inhibited by chaperonin 60, with which the unfolded or partly folded Rubisco forms a stable binary complex. The chaperonin-dependent reconstitution of Rubisco involves the formation of a complex between chaperonin 60 and chaperonin 10 (groES). Formation of this complex almost completely inhibits the uncoupled ATPase activity of chaperonin 60. Furthermore, although the formation of the chaperonin 60-chaperonin 10 complex requires the presence of MgATP, hydrolysis of ATP may not be required, since complex formation occurs in the absence of K+. The interaction of chaperonin 60 with unfolded or partly folded Rubisco does not require MgATP, K+, or chaperonin 10. However, discharge of the complex of chaperonin 60-Rubisco, which leads to the formation of active Rubisco dimers, requires chaperonin 10 and a coupled, K(+)-dependent hydrolysis of ATP. We propose that a role of chaperonin 10 is to couple the K(+)-dependent hydrolysis of ATP to the release of the folded monomers of the target protein from chaperonin 60.
Adenosine Triphosphatases/metabolism, Adenosine Triphosphate/pharmacology, Bacterial Proteins/metabolism, Chaperonins, Escherichia coli/drug effects, Escherichia coli/metabolism, Hydrolysis, Potassium/pharmacology, Protein Conformation, Proteins/metabolism, Ribulose-Bisphosphate Carboxylase/metabolism, Temperature
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