title: Archazolid and apicularen: novel specific V-ATPase inhibitors.
abstract: BACKGROUND
  V-ATPases constitute a ubiquitous family of heteromultimeric, proton translocating proteins. According to their localization in a multitude of eukaryotic membranes, they energize many different transport processes. Since their malfunction is correlated with various diseases in humans, the elucidation of the properties of this enzyme for the development of selective inhibitors and drugs is one of the challenges in V-ATPase research.
  
  
  RESULTS
  Archazolid A and B, two recently discovered cytotoxic macrolactones produced by the myxobacterium Archangium gephyra, and apicularen A and B, two novel benzolactone enamides produced by different species of the myxobacterium Chondromyces, exerted a similar inhibitory efficacy on a wide range of mammalian cell lines as the well established plecomacrolidic type V-ATPase inhibitors concanamycin and bafilomycin. Like the plecomacrolides both new macrolides also prevented the lysosomal acidification in cells and inhibited the V-ATPase purified from the midgut of the tobacco hornworm, Manduca sexta, with IC50 values of 20-60 nM. However, they did not influence the activity of mitochondrial F-ATPase or that of the Na+/K+-ATPase. To define the binding sites of these new inhibitors we used a semi-synthetic radioactively labelled derivative of concanamycin which exclusively binds to the membrane Vo subunit c. Whereas archazolid A prevented, like the plecomacrolides concanamycin A, bafilomycin A1 and B1, labelling of subunit c by the radioactive I-concanolide A, the benzolactone enamide apicularen A did not compete with the plecomacrolide derivative.
  
  
  CONCLUSIONS
  The myxobacterial antibiotics archazolid and apicularen are highly efficient and specific novel inhibitors of V-ATPases. While archazolid at least partly shares a common binding site with the plecomacrolides bafilomycin and concanamycin, apicularen adheres to an independent binding site.
authors.affiliation: Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Tierphysiologie, 49069 Osnabrück, Germany. huss@biologie.uni-osnabrueck.de
authors.forename: Markus
authors.initials: M
authors.lastname: Huss
authors.forename: Florenz
authors.initials: F
authors.lastname: Sasse
authors.forename: Brigitte
authors.initials: B
authors.lastname: Kunze
authors.forename: Rolf
authors.initials: R
authors.lastname: Jansen
authors.forename: Heinrich
authors.initials: H
authors.lastname: Steinmetz
authors.forename: Gudrun
authors.initials: G
authors.lastname: Ingenhorst
authors.forename: Axel
authors.initials: A
authors.lastname: Zeeck
authors.forename: Helmut
authors.initials: H
authors.lastname: Wieczorek
mesh_terms: D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D002417:Cattle; D002460:Cell Line; D018942:Macrolides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D018402:Manduca; D051379:Mice; D011480:Protease Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013379:Substrate Specificity; D013552:Swine; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018942:Macrolides; D011480:Protease Inhibitors; C117813:apicularen A; C117814:apicularen B; C453562:macrolactin A; D025262:Vacuolar Proton-Translocating ATPases