PRODIGIOSINS UNCOUPLE MITOCHONDRIAL AND BACTERIAL F-ATPASES - EVIDENCE FOR THEIR H+ CL- SYMPORT ACTIVITY/

Prodigiosin, metacycloprodigiosin, and prodigiosin 25-C all inhibited the acidification activity of submitochondrial and bacterial (Escheric hia coli) F-ATPases (F0F1-ATPases) strongly (IC50 =20-30 and 24-30 pmo l/mg protein, respectively), without affecting significantly the ATP h ydrolysis activity, Their effect on the acidification activity was rap id and reversible, showing non-competitive apparent K-i values of the order of nM to sub-nM, However, unlike FCCP (an ordinary uncoupler of oxidative phosphorylation), they showed no protonophoric activity, as demonstrated by the absence of acceleration of ATP hydrolysis. Prodigi osins also inhibited the acidification of proteoliposomes reconstitute d from phospholipids and purified F-ATPase of E. coli, suggesting that their acidification-inhibitory effect is not due to the inhibition of anion channels, They did not, however, inhibit the ATP-dependent form ation of membrane potential of F-ATPase vesicles, Furthermore, they in hibited and quickly reversed acidification by F-ATPase only in the pre sence of chloride, and not in the presence of gluconate anion, Finally , they induced swelling of liposomes and submitochondrial particles in isotonic solution of ammonium chloride but not ammonium gluconate, su ggesting that intravesicular entry of Cl- is promoted by prodigiosins, These results suggest that prodigiosins uncouple F-ATPases through pr omotion of H+/Cl- symport (or OH-/Cl- exchange) across vesicular membr anes.