Photoaffinity cross‐linking of F₁ATPase from the thermophilic bacterium PS3 by 3′‐arylazido‐β‐alanyl‐2‐azido ATP

Abstract

The photoactivatable bifunctional 3′‐arylazido‐β‐alanyl‐2‐azido ATP (2,3′‐DiN 3 ATP) has been applied to study the localization of the nucleotide‐binding sites of coupling factor 1 (F 1 ATPase, TF 1 ) from the thermophilic bacterium PS3 by photoaffinity cross‐linking. UV irradiation of TF 1 in the presence of 2,3′‐DiN 3 ATP results in the nucleotide‐dependent formation of various higher molecular mass cross‐links formed by two, three or even four α‐ and/or β‐subunits. The differences observed upon photoaffinity cross‐linking by the bifunctional 2‐azido ATP or 8‐azido ATP analog are discussed. They are probably due to the varied maximal distance between both azido groups, or to the different conformations ( anti/syn ) of these analogs. The results confirm our suggestion that several (possibly all) nucleotide‐binding sites of F 1 ATPases are located at the interfaces between α‐ and β‐subunits.