ATP-triggered ADP release from the asymmetric chaperonin GroEL/GroES/ADP7 is not the rate-limiting step of the GroEL/GroES reaction cycle.
The GroEL/GroES protein folding chamber is formed and dissociated by ATP binding and hydrolysis. ATP hydrolysis in the GroES-bound (cis) ring gates entry of ATP into the opposite unoccupied trans ring, which allosterically ejects cis ligands. While earlier studies suggested that hydrolysis of cis ATP is the rate-limiting step of the cycle (t1/2 approximately 10 s), a recent study suggested that ADP release from the cis ring may be rate-limiting (t1/2 approximately 15-20 s). Here we have measured ADP release using a coupled enzyme assay and observed a t1/2 for release of <or=4-5 s, indicating that this is not the rate-limiting step of the reaction cycle.
Tyagi
Navneet K
NK
Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, Boyer Center, 295 Congress Avenue, New Haven, CT 06510, USA.
Fenton
Wayne A
WA
Horwich
Arthur L
AL
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D018835:Chaperonin 10 / Q000235:genetics / Q000378:metabolism*; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism*; D018833:Chaperonins / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008954:Models, Biological; D011485:Protein Binding; D017510:Protein Folding
D018835:Chaperonin 10; D018834:Chaperonin 60; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D018833:Chaperonins