TY - JOUR
T1 - Comparison of energization of complex I in membrane particles from Paracoccus denitrificans and bovine heart mitochondria
AU - Kotlyar, Alexander
AU - Albracht, Simon P.J.
AU - Van Spanning, Rob J.M.
N1 - Funding Information:
The investigationws ere supported(i n part) by the Netherlands Foundation for Chemical Research (SON) with financial aid from the NetherlandsO r-ganizationf or Scientific Research (NWO), and by EU Grant BIO2-CT-93-0364.
PY - 1998/6/10
Y1 - 1998/6/10
N2 - The results of preliminary studies of the effects of energization on the catalytic and EPR properties of complex I in tightly coupled membrane vesicles of Paracoccus denitrificans (SPP) are presented. They are compared to those observed in submitochondrial particles from bovine heart (SMP). All signs of energization of complex I detected by EPR in SMP (uncoupler- sensitive splitting of the g(z) lines of the clusters 2 and a broadening of their g(xy) lines, a fast-relaxing, piericidin-sensitive ubiquinone-radical signal, and a broad signal around g=1.94) were also observed with the bacterial enzyme. There were some prominent differences, though. The signal of the fast-relaxing radicals could be evoked both in the presence or absence of reduced clusters 2, suggesting that enhancement of its spin-relaxation rate is caused by coupling to another paramagnet. The signal was hardly affected by the presence of gramicidin. The slow-relaxing radical signal did not disappear upon anaerobiosis, but was detectable for at least another 30 s. The fast-relaxing signal vanished immediately upon anaerobiosis. The activity of the bacterial enzyme during oxidation of NADH by oxygen or reduction of NAD induced by succinate oxidation, was 5-6 times higher than that of the mitochondrial enzyme. Unlike the mitochondrial enzyme, the bacterial enzyme was not inactivated by incubation at 35°C. The spin concentration of the NADH-reducible [2Fe-2S] cluster (1b) was half that of the clusters 2, indicating no difference with the mitochondrial enzyme.
AB - The results of preliminary studies of the effects of energization on the catalytic and EPR properties of complex I in tightly coupled membrane vesicles of Paracoccus denitrificans (SPP) are presented. They are compared to those observed in submitochondrial particles from bovine heart (SMP). All signs of energization of complex I detected by EPR in SMP (uncoupler- sensitive splitting of the g(z) lines of the clusters 2 and a broadening of their g(xy) lines, a fast-relaxing, piericidin-sensitive ubiquinone-radical signal, and a broad signal around g=1.94) were also observed with the bacterial enzyme. There were some prominent differences, though. The signal of the fast-relaxing radicals could be evoked both in the presence or absence of reduced clusters 2, suggesting that enhancement of its spin-relaxation rate is caused by coupling to another paramagnet. The signal was hardly affected by the presence of gramicidin. The slow-relaxing radical signal did not disappear upon anaerobiosis, but was detectable for at least another 30 s. The fast-relaxing signal vanished immediately upon anaerobiosis. The activity of the bacterial enzyme during oxidation of NADH by oxygen or reduction of NAD induced by succinate oxidation, was 5-6 times higher than that of the mitochondrial enzyme. Unlike the mitochondrial enzyme, the bacterial enzyme was not inactivated by incubation at 35°C. The spin concentration of the NADH-reducible [2Fe-2S] cluster (1b) was half that of the clusters 2, indicating no difference with the mitochondrial enzyme.
KW - Complex I
KW - Energization
KW - Mitochondrion
KW - NADH:Q oxidoreductase
KW - Paracoccus denitrificans
UR - http://www.scopus.com/inward/record.url?scp=0032321581&partnerID=8YFLogxK
U2 - 10.1016/S0005-2728(98)00042-5
DO - 10.1016/S0005-2728(98)00042-5
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AN - SCOPUS:0032321581
SN - 0005-2728
VL - 1365
SP - 53
EP - 59
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 1-2
ER -