Elastic rotation of Escherichia coli F(O)F(1) having ε subunit fused with cytochrome b(562) or flavodoxin reductase.

Highlights: • Intra-molecular rotation of F{sub O}F{sub 1} ATP synthase was observed using a small bead probe. • Carboxyl-terminus of the e subunit was fused to cytochrome b{sub 562} or flavodoxin reductase. • The F{sub O}F{sub 1} showed continual rotation with similar rate to the wild-type enzyme. • The intra-molecular rotation is flexible and elastic. - Abstract: Intra-molecular rotation of F{sub O}F{sub 1} ATP synthase enables cooperative synthesis and hydrolysis of ATP. In this study, using a small gold bead probe, we observed fast rotation close to the real rate that would be exhibited without probes. Using this experimental system, we tested the rotation of F{sub O}F{sub 1} with the e subunit connected to a globular protein [cytochrome b{sub 562} (e-Cyt) or flavodoxin reductase (e-FlavR)], which is apparently larger than the space between the central and the peripheral stalks. The enzymes containing e-Cyt and e-FlavR showed continual rotations with average rates of 185 and 148 rps, respectively, similar to the wild type (172 rps). However, the enzymes with e-Cyt or e-FlavR showed a reduced proton transport. These results indicate that the intra-molecular rotation is elastic but proton transport requires more strict subunit/subunit interaction.