TY - JOUR
T1 - The mitochondrial respiratory chain of Ustilago maydis
AU - Juárez, Oscar
AU - Guerra, Guadalupe
AU - Martínez, Federico
AU - Pardo, Juan Pablo
N1 - Funding Information:
The authors thank Dr. F. Bannuett, from the University of California, for the strain FB 2 of wild-type Ustilago maydis, and Dr. Diego Gonzalez-Halphen from Instituto de Fisiología Celular, UNAM, for the rabbit antiserum against Clamydomonas reindhartii AOX, and Dr. R. Muñoz-Clares and Dr. M. Calcagno for stimulating discussions. This work was partially supported by Grants 37263M (FM) and 44564 (JPP) from CONACyT and IN238402 from DGAPA (JPP).
PY - 2004/10/4
Y1 - 2004/10/4
N2 - Ustilago maydis mitochondria contain the four classical components of the electron transport chain (complexes I, II, III, and IV), a glycerol phosphate dehydrogenase, and two alternative elements: an external rotenone-insensitive flavone-sensitive NADH dehydrogenase (NDH-2) and an alternative oxidase (AOX). The external NDH-2 contributes as much as complex I to the NADH-dependent respiratory activity, and is not modulated by Ca 2+, a regulatory mechanism described for plant NDH-2, and presumed to be a unique characteristic of the external isozyme. The AOX accounts for the 20% residual respiratory activity after inhibition of complex IV by cyanide. This residual activity depends on growth conditions, since cells grown in the presence of cyanide or antimycin A increase its proportion to about 75% of the uninhibited rate. The effect of AMP, pyruvate and DTT on AOX was studied. The activity of AOX in U. maydis cells was sensitive to AMP but not to pyruvate, which agrees with the regulatory characteristics of a fungal AOX. Interestingly, the presence of DTT during cell permeabilisation protected the enzyme against inactivation. The pathways of quinone reduction and quinol oxidation lack an additive behavior. This is consistent with the competition of the respiratory components of each pathway for the quinol/quinone pool.
AB - Ustilago maydis mitochondria contain the four classical components of the electron transport chain (complexes I, II, III, and IV), a glycerol phosphate dehydrogenase, and two alternative elements: an external rotenone-insensitive flavone-sensitive NADH dehydrogenase (NDH-2) and an alternative oxidase (AOX). The external NDH-2 contributes as much as complex I to the NADH-dependent respiratory activity, and is not modulated by Ca 2+, a regulatory mechanism described for plant NDH-2, and presumed to be a unique characteristic of the external isozyme. The AOX accounts for the 20% residual respiratory activity after inhibition of complex IV by cyanide. This residual activity depends on growth conditions, since cells grown in the presence of cyanide or antimycin A increase its proportion to about 75% of the uninhibited rate. The effect of AMP, pyruvate and DTT on AOX was studied. The activity of AOX in U. maydis cells was sensitive to AMP but not to pyruvate, which agrees with the regulatory characteristics of a fungal AOX. Interestingly, the presence of DTT during cell permeabilisation protected the enzyme against inactivation. The pathways of quinone reduction and quinol oxidation lack an additive behavior. This is consistent with the competition of the respiratory components of each pathway for the quinol/quinone pool.
KW - Alternative NADH dehydrogenase
KW - Alternative oxidase
KW - Basidiomycete
KW - Digitonin
KW - Electron transport chain
KW - Permeabilisation
KW - Salicylhydroxamic acid
KW - Ustilago maydis
UR - http://www.scopus.com/inward/record.url?scp=4644285224&partnerID=8YFLogxK
U2 - 10.1016/j.bbabio.2004.06.005
DO - 10.1016/j.bbabio.2004.06.005
M3 - Artículo
SN - 0005-2728
VL - 1658
SP - 244
EP - 251
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 3
ER -