Fumonisin B1, a sphingoid toxin, is a potent inhibitor of the plasma membrane H+-ATPase
Por:
Gutiérrez-Nájera N., Muñoz-Clares R.A., Palacios-Bahena S., Ramírez J., Sánchez-Nieto S., Plasencia J., Gavilanes-Ruíz M.
Publicada:
1 ene 2005
Resumen:
Fumonisin B1 (FB1) 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 ?M inhibited root elongation by 50% and at 30 ?M decreased medium acidification by about 80%. Irrespective of the presence and absence of FB1, 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 FB1 is a total uncompetitive inhibitor of this enzyme with an inhibition constant value of 17.5±1 ?M. Thus FB1 decreased V max and increased the apparent affinity of the enzyme for ATP-Mg to the same extent. Although FB1 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 FB1-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 FB1 but also by its structural analogs, the sphingoid intermediates, which accumulate upon the inhibition of sphinganine N-acyltransferase by this toxin. © Springer-Verlag 2005.
Filiaciones:
Gutiérrez-Nájera N.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
Muñoz-Clares R.A.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
Palacios-Bahena S.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
Ramírez J.:
Departamento de Genética Molecular, Instituto de Fisiología Celular, UNAM, Apdo Postal 70242, 04510 México DF, Mexico
Sánchez-Nieto S.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
Plasencia J.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
Gavilanes-Ruíz M.:
Departamento de Bioquímica, Conj. E. Facultad de Química, UNAM Cd. Universitaria, 04510 México DF, Mexico
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