Cercospora beticola toxins. Part XVII. The role of the beticolin/Mg2+ complexes in their biological activity. Study of plasma membrane H(+)-ATPase, vacuolar H(+)-PPase, alkaline and acid phosphatases.
Beticolin-1 and beticolin-2, yellow toxins produced by the phytopathogenic fungus Cercospora beticola, inhibit the plasma membrane H(+)-ATPase. Firstly, since beticolins are able to form complexes with Mg2+, the role of the beticolin/Mg2+ complexes in the inhibition of the plasma membrane proton pump has been investigated. Calculations indicate that beticolins could exist under several forms, in the H(+)-ATPase assay mixture, both free or complexed with Mg2+. However, the percentage inhibition of the H(+)-ATPase activity is correlated to the concentration of one single form of beticolin, the dimeric neutral complex Mg2H2B2, which appears to be the active form involved in the H(+)-ATPase inhibition. Secondly, since previous data suggested that beticolins could also be active against other Mg2(+)-dependent enzymes, we tested beticolin-1 on the vacuolar H(+)-PPase, which requires Mg2+ as co-substrate, and on the alkaline and acid phosphatases, which do not use Mg2+ as co-substrate. Only vacuolar H(+)-PPase is sensitive to beticolin-1, which suggests that beticolins are specific to enzymes that use a complex of Mg2+ as the substrate. The same Mg2H2B2 complex which is responsible of the plasma membrane H(+)-ATPase inhibition appears to be also involved in the inhibition of the vacuolar H(+)-PPase.
Gomès
E
E
Laboratoire de Phytopharmacie, UA 692 INRA/Université de Bourgogne, Dijon, France.
Gordon-Weeks
R
R
Simon-Plas
F
F
Pugin
A
A
Milat
M L
ML
Leigh
R A
RA
Blein
J P
JP
D000135:Acid Phosphatase / Q000037:antagonists & inhibitors; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006576:Heterocyclic Compounds, 4 or More Rings; D043564:Inorganic Pyrophosphatase; D008274:Magnesium / Q000737:chemistry* / Q000502:physiology; D009183:Mycotoxins / Q000737:chemistry / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors*; D011755:Pyrophosphatases / Q000037:antagonists & inhibitors*; D014617:Vacuoles / Q000201:enzymology; D003313:Zea mays
D004791:Enzyme Inhibitors; D006576:Heterocyclic Compounds, 4 or More Rings; D009183:Mycotoxins; C089994:beticolin 2; C089993:beticolin 1; D000469:Alkaline Phosphatase; D000135:Acid Phosphatase; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase; D006180:Proton-Translocating ATPases; D008274:Magnesium