Topography in relation to activity of the F1-ATPase of Micrococcus lysodeikticus (M. luteus): a study using trypsin...

Micrococcus lysodeikticus (M. luteus) ATPase digested in a controlled manner with trypsin behaves like the native protein when chromatographed on alkyl agarose supports. The enzyme immobilized on the supports through noncovalent interaction is able to hydrolyze ATP with a specific activity similar to that of native membrane-bound ATPase. However, the response of M. lysodeikticus ATPase to the interaction with the hydrophobic columns can be modified by changing the protein-ligand ratio. These results support the notion that the catalytic site of M. lysodeikticus ATPase is not involved in the interaction with alkyl agarose, but rather that binding of the ATPase to the hydrophobic columns takes place through polypeptide or protein domains other than those which mediate binding to the native membranes, since they are very easily modified by trypsin. It is proposed that the alpha subunit plays a role in the interaction of the bacterial ATPase with hydrophobic ligands. These results are discussed in relation to the topography of the enzyme as established previously.