8-N(3)-3'-biotinyl-ATP, a novel monofunctional reagent: differences in the F(1)- and V(1)-ATPases by means of the ATP analogue.

A novel photoaffinity label, 8-N(3)-3'-biotinyl-ATP, has been synthesized. The introduction of an additional biotin residue is advantageous for easy detection of labeled proteins. This could be first tested by reaction with the F(1)-ATPase from the thermophilic bacterium PS3 (TF(1)). UV irradiation of TF(1) in the presence of 8-N(3)-3'-biotinyl-ATP results in a nucleotide-dependent binding of the analogue in the noncatalytic alpha and the catalytic beta subunits of TF(1), demonstrating the suitability of this analogue as a potential photoaffinity label. Reaction with the V(1)-ATPase, however, led to labeling of subunit E, which has been suggested as a structural and functional homologue of the gamma subunit of the F-ATPases. MALDI-TOF mass spectrometry has been used to map the regions of subunit E involved in the binding of 8-N(3)-3'-biotinyl-ATP.