ATP synthesis and hydrolysis of the ATP-synthase from Micrococcus luteus regulated by an inhibitor subunit and membrane energization

After incubation for 70 min in Tris-HCl (pH 8.0), the rate of ATP hydrolysis of free and reconstituted ATP-synthase from Micrococcus luteus multiplied about three times. The apparent increase in activity is due to the reversible dissociation of the δ-subunit. Results of experiments on the temperature dependence of the ATP hydrolysis rate of substrate saturated ATP-synthase exhibited a discontinuity in the Arrhenius plot at 32 ± 0.5°C for the δ-subunit associated enzyme. Below 32 ± 0.5°C the activation energy, E_a, was 231.5 ± 5 kJ mol^-1, while above this temperature-level it decreased to 76.4 ± 3 kJ mol^-1. ATP synthesis and hydrolysis of the ATP-synthase, co-reconstituted with monomeric bacteriorhodopsin (Halobacterium halobium), showed a lag of 50 s upon the illumination with green light (505-575 nm). This retardation and the activity depended on the ATP-synthase concentration, being typical of the dissociation of an inhibitor protein. The N-terminal protein sequences of the δ-and ε{lunate}-subunit of the ATP-synthase were identified by automated Edman degradation. Alignment of the amino acid sequence and secondary structure calculations for the δ-subunit did not reveal homology to other known ATP-synthase δ-subunits, but significant equivalence to the ε{lunate}-subunit of E. coli. Sequence analysis of the ε{lunate}-subunit from M. luteus showed homology to equivalent regions in δ-subunits and Oligomycin Sensitivity Conferring Protein (OSCP) of other organisms.