Fumonisin B1, a sphingoid toxin, is a potent inhibitor of the plasma membrane H+-ATPase

Abstract

Fumonisin B(1) (FB(1)) is an amphipathic toxin produced by the pathogenic fungus Fusarium verticillioides which causes stem, root and ear rot in maize (Zea mays L.). In this work, we studied the action of FB(1) on the plasma membrane H(+)-ATPase (EC 3.6.1.34) from germinating maize embryos, and on the fluidity and lipid peroxidation of these membranes. In maize embryos the toxin at 40 microM inhibited root elongation by 50% and at 30 microM decreased medium acidification by about 80%. Irrespective of the presence and absence of FB(1), the H(+)-ATPase in plasma membrane vesicles exhibited non-hyperbolic saturation kinetics by ATPH-Mg, with Hill number of 0.67. Initial velocity studies revealed that FB(1) is a total uncompetitive inhibitor of this enzyme with an inhibition constant value of 17.5+/-1 microM. Thus FB(1) decreased V(max) and increased the apparent affinity of the enzyme for ATP-Mg to the same extent. Although FB(1) increased the fluidity at the hydrophobic region of the membrane, no correlation was found with its effect on enzyme activity, since both effects showed different FB(1)-concentration dependence. Peroxidation of membrane lipids was not affected by the toxin. Our results suggest that, under in vivo conditions, the plasma membrane H(+)-ATPase is a potentially important target of the toxin, as it is inhibited not only by FB(1) but also by its structural analogs, the sphingoid intermediates, which accumulate upon the inhibition of sphinganine N-acyltransferase by this toxin.

The puzzle of bakanae disease through interactions between Fusarium fujikuroi and rice

“…The main fumonisin (FB 1 ) inhibits the enzyme ceramide synthase, which is included in sphingolipid biosynthesis in plants and animals. This affects the cell function and may result in cell autolysis and inhibition of the plasma membrane ATPase (40).…”

The Role of the Plasma Membrane H+-ATPase in Plant–Microbe Interactions

“…FB1 is a sphingoid toxin, structurally related to AAL-toxin produced by Alternaria alternata, and shares similar properties in its animal toxicity. FB1 has several reported toxic effects on cellular function, one of which is significant inhibition of the PM H + -ATPase and other P-type ATPases (Abbas et al, 1994;Gutié rrez-Ná jera et al, 2005). Due to its amphiphilic chemical structure, FB1 can insert into lipid bilayers and enhance membrane fluidity (Ferrante et al, 2002;Gutié rrez-Ná jera et al, 2005).…”

“…FB1 has several reported toxic effects on cellular function, one of which is significant inhibition of the PM H + -ATPase and other P-type ATPases (Abbas et al, 1994;Gutié rrez-Ná jera et al, 2005). Due to its amphiphilic chemical structure, FB1 can insert into lipid bilayers and enhance membrane fluidity (Ferrante et al, 2002;Gutié rrez-Ná jera et al, 2005). Therefore, its inhibitory effect on the PM H + -ATPase is likely indirect and a consequence of membrane disruption that leads to aberrant enzyme function.…”

Plant lipid environment and membrane enzymes: the case of the plasma membrane H+-ATPase

“…The inclusion of Fumonisin B 1 (FB 1 ), a fungal toxin, into the plasma membrane increased its fluidity but there was no correlation with the PM H ? -ATPase activity since both events exhibited a different FB 1 concentration dependence (Gutiérrez-Nájera et al 2005). Also, treated plants with abscisic acid (ABA) or gibberellic acid (GA3) exhibited increased plasma membrane fluidity and decreased the PM H ?…”