70] Modifiers of F1-ATPases and associated peptides

Abstract

This chapter describes the modifiers of F1-ATPases and the associated peptides. The chemical modifiers of proteins can be divided into two classes—the group-directed reagents (chemical reagents capable of binding to side-chain residues in the investigated protein); and the active site-directed reagents (affinity and photoaffinity labels). The mitochondrial, bacterial, and chloroplast ATPases are H + -dependent ATPases (ATP synthases), as they catalyze both ATP hydrolysis and synthesis. Dicyclohexylcarbodiimide (DCCD) is used as a chemical reagent to block the proton conduction in the F 0 channel of the ATPase complex at the level of the DCCD-binding protein. Intermolecular cross-linking by random collisions between independent F 1 molecules is not predominant at the protein concentrations used for chemical modification. Intramolecular cross-linking can establish bridges in a single subunit (hairpin formation) or between two adjacent subunits but the cross-linking requires higher concentrations of reagents than inactivation.