ATP-driven stepwise rotation of FoF1-ATP synthase
AUTOR(ES)
Ueno, Hiroshi
FONTE
National Academy of Sciences
RESUMO
FoF1-ATP synthase (FoF1) is a motor enzyme that couples ATP synthesis/hydrolysis with a transmembrane proton translocation. F1, a water-soluble ATPase portion of FoF1, rotates by repeating ATP-waiting dwell, 80° substep rotation, catalytic dwell, and 40°-substep rotation. Compared with F1, rotation of FoF1 has yet been poorly understood, and, here, we analyzed ATP-driven rotations of FoF1. Rotation was probed with an 80-nm bead attached to the ring of c subunits in the immobilized FoF1 and recorded with a submillisecond fast camera. The rotation rates at various ATP concentrations obeyed the curve defined by a Km of ≈30 μM and a Vmax of ≈350 revolutions per second (at 37°C). At low ATP, ATP-waiting dwell was seen and the kon-ATP was estimated to be 3.6 × 107 M-1·s-1. At high ATP, fast, poorly defined stepwise motions were observed that probably reflect the catalytic dwells. When a slowly hydrolyzable substrate, adenosine 5′-[γ-thio]triphosphate, was used, the catalytic dwells consisting of two events were seen more clearly at the angular position of ≈80°. The rotational behavior of FoF1 resembles that of F1. This finding indicates that “friction” in Fo motor is negligible during the ATP-driven rotation. Tributyltin chloride, a specific inhibitor of proton translocation, slowed the rotation rate by 96%. However, dwells at clearly defined angular positions were not observed under these conditions, indicating that inhibition by tributyltin chloride is complex.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=545493Documentos Relacionados
- 36° step size of proton-driven c-ring rotation in FoF1-ATP synthase
- Subunit rotation in Escherichia coli FoF1–ATP synthase during oxidative phosphorylation
- Mechanism of Inhibition by C-terminal α-Helices of the ϵ Subunit of Escherichia coli FoF1-ATP Synthase*
- ATP-driven sodium pump in Streptococcus faecalis.
- ATP-driven calcium transport in membrane vesicles of Streptococcus sanguis.