Effects of energization and substrates on the reactivities of lysine residues of the chloroplast ATP synthase beta subunit.

The incubation of chloroplast thylakoids with pyridoxal 5'-phosphate for a short time (5 s) modified the lysine residues of the ATP synthase beta subunit. Except for lysine residues in the N-terminal and C-terminal regions, the glycine-rich P-loop (GGAGVGKT)-, Lys154-, and Lys167-containing peptide (P-peptide) exhibited high reactivity with pyridoxal 5'-phosphate. The energization of thylakoids or addition of substrates (ADP, Pi, ATP) affected the modifications of the P-peptide, Lys447, and Lys399. For the P-peptide, substrates inhibited the modification with 0.5 mM ADP inhibiting by 80%. Energization enhanced the inhibitory effects of substrates. For Lys447, substrates also inhibited the modification; 0.5 mM ADP inhibited by 60%. For Lys399, the reactivity depended on the transmembrane delta mu H+. With increasing delta mu H+, the reactivity decreased. These results suggest the existence of energy-dependent conformational changes at the catalytic nucleotide-binding site and around Lys399. The former increases the affinity of the site for substrates. Substrate binding at the catalytic site changes the conformation around Lys447.