ADP TETHERED TO TYROSINE-BETA-345 AT THE CATALYTIC SITE OF THE BOVINEHEART F1-ATPASE IS CONVERTED TO TETHERED AMP BY MG2-DEPENDENT HYDROLYSIS WHEN THE ENZYME IS PHOTOINACTIVATED WITH 2-N-3-ADP()

Comparison of profiles of radioactive peptides resolved by HPLC from t ryptic digests of the bovine heart F-1-ATPase depleted of nucleotides (nd-MF(1)) which had been photoinactivated with 2-N-3-[beta-P-32]ADP, on the one hand, and 2-[8-H-3]ADP, on the other, shows that the beta p hosphate of ADP tethered to tyrosine-beta 345 is slowly hydrolyzed in the presence of Mg2+. When nd-MF(1) was photoinactivated with 2-N-3-[8 -H-3]ADP in the absence of Mg2+, hydrolysis of the beta phosphate from ADP tethered to tyrosine-beta 345 was not observed. Subsequent additi on of Mg2+ initiated conversion of ADP tethered to tyrosine-beta 345 t o tethered AMP suggesting that functional groups at the catalytic site participate in the hydrolytic reaction.