Nucleotide Exchange from the High-Affinity ATP-Binding Site in SecA is the Rate-Limiting Step in the ATPase Cycle of the Soluble Enzyme and Occurs through a Specialized Conformational State
We have characterized the kinetic and thermodynamic consequences of adenine nucleotide interaction with the low-affinity and high-affinity nucleotide-binding sites in free SecA. ATP binds to the hydrolytically active high-affinity site approximately 3-fold more slowly than ADP when SecA is in its conformational ground state, suggesting that ATP binding probably occurs when the enzyme is in another conformational state during the productive ATPase/transport
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