ATP-triggered ADP release from the asymmetric chaperonin GroEL/GroES/ADP7 is not the rate-limiting step of the GroEL/GroES reaction cycle |
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Authors: | Navneet K Tyagi Wayne A Fenton |
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Institution: | a Howard Hughes Medical Institute, Yale University School of Medicine, Boyer Center, 295 Congress Avenue, New Haven, CT 06510, USA b Department of Genetics, Yale University School of Medicine, Boyer Center, 295 Congress Avenue, New Haven, CT 06510, USA |
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Abstract: | 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 (t½ ∼ 10 s), a recent study suggested that ADP release from the cis ring may be rate-limiting (t½ ∼ 15-20 s). Here we have measured ADP release using a coupled enzyme assay and observed a t½ for release of ?4-5 s, indicating that this is not the rate-limiting step of the reaction cycle. |
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Keywords: | DTT dithiothreitol HEPES N-(2-hydroxyethyl)piperazine-N&prime -(2-ethanesulfonic acid) LDH lactate dehydrogenase PEP phosphoenol pyruvate PK pyruvate kinase |
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