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 hydr olysis 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 delta-subunit. Results of exper iments on the temperature dependence of the ATP hydrolysis rate of sub strate saturated ATP-synthase exhibited a discontinuity in the Arrheni us plot at 32 +/- 0.5 degrees C for the delta-subunit associated enzym e. Below 32 +/- 0.5 degrees 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 halo bium), showed a lag of 50 s upon the illumination with green light (50 5-575 nm). This retardation and the activity depended on the ATP-synth ase concentration, being typical of the dissociaton of an inhibitor pr otein. The N-terminal protein sequences of the delta- and epsilon-subu nit of the ATP-synthase were identified by automated Edman degradation . Alignment of the amino acid sequence and secondary structure calcula tions for the delta-subunit did not reveal homology to other known ATP -synthase delta-subunits, but significant equivalence to the epsilon-s ubunit of E. coli. Sequence analysis of the epsilon-subunit from M. lu teus showed homology to equivalent regions in delta-subunits and Oligo mycin Sensitivity Conferring Protein (OSCP) of other organisms.