Semisynthetic derivatives of concanamycin A and C, as inhibitors of V- and P-type ATPases:: Structure-activity investigations and developments of photoaffinity probes

V-type ATPases are inhibited by the plecomacrolides bafilomycin and concanamycin, which exert their inhibitory potential at nanomolar concentrations. In addition, some P-type ATPases are inhibited at micromolar concentrations. We initiated intensive structure-activity investigations with semisynthetic concanamycin derivatives to approach the following two questions: (i) What is the pharmacophor, the structural key element, of the plecomacrolides that leads to their inhibitory potential against V- and P-type ATPases? (ii) Where is the binding site within these two different types of ATPases? In a first step, we examined where chemical modifications (O-acylations, substitutions, eliminations) could be placed without seriously affecting the inhibitory potential of the macrolides. In a second step, we used the knowledge of these structure-activity investigations to introduce traceable elements (fluorescent or radioactive) or nitrene-generating azido or carbene-generating diazirine-groups able to bind the inhibitors to their target covalently. These studies led finally to the synthesis of two photoaffinity probes that were used in labeling experiments with the purified plasma membrane V-type ATPase of Manduca sexta (described in a following paper, Huss, M., Gassel, M., Ingenhorst, G., Drose, S., Zeeck, A., Altendorf, K., Wieczorek, H., manuscript submitted).