Abstract
Comparison of profiles of radioactive peptides resolved by HPLC from tryptic digests of the bovine heart F1‐ATPase depleted of nucleotides (nd‐MF1) which had been photoinactivated with 2‐N3‐[β‐32P]ADP, on the one hand, and 2‐[8‐3H]ADP, on the other, shows that the β phosphate of ADP tethered to tyrosine‐β345 is slowly hydrolyzed in the presence of Mg2+. When nd‐MF1 was photoinactivated with 2‐N3‐[8‐3H]ADP in the absence of Mg2+, hydrolysis of the β phosphate from ADP tethered to tyrosine‐β345 was not observed. Subsequent addition of Mg2+ initiated conversion of ADP tethered to tyrosine‐β345 to tethered AMP suggesting that functional groups at the catalytic site participate in the hydrolytic reaction.