Open AccessBinding and Screening by Cations and the Effect on Exogenous NAD(P)H Oxidation in Neurospora crassa Mitochondria
Author(s) -
MOLLER Ian M.,
SCHWITZGUEBEL JeanPaul,
PALMER John M
Publication year - 1982
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1982.tb06501.x
Subject(s) - neurospora crassa , neurospora , mitochondrion , nad+ kinase , biochemistry , helianthus , redox , biology , chemistry , enzyme , inorganic chemistry , gene , sunflower , mutant , agronomy
1 The uncoupled oxidation of exogenous NADH by mitochondria from Neurospora crassu has a pH optimum at 7.0. In the presence of EDTA (1 mM) the optimum is at pH 6.5; maximal inhibition (65%) occurs at pH 7.2. This is comparable to the results with higher plant mitochondria. 2 The corresponding pH optima for NADPH oxidation are 7.75 (control), 7.0 (+ EDTA) and 8.0 (effect of EDTA), respectively. NADPH oxidation is completely inhibited by EDTA at pH 8.0. These pH optima are all about 1 higher than observed in mitochondria from higher plants. 3 The inhibition of NADH oxidation by EDTA is shown to be due to the removal of Mg 2+ bound to the mitochondria1 membranes. 4 It is shown that 9‐aminoacridine can be used to monitor the surface potential of the membranes of Neurospora mitochondria. 5 Cations stimulate NADH oxidation by Neurospora mitochondria in a manner consistent with the theory of the diffuse layer. Quantitatively, the rcsults suggest that Neurospora mitochondria contain fewer charges per mass of protein than Jerusalem artichoke ( Heliantthus tuberosus ) mitochondria but more than mitochondria from Arum maculatum spadices. 6 A good correlation is found between the effect of La 3+ on the fluorescence of 9‐aminoacridine in the presence of mitochondria and on the oxidation of NADH by the mitochondria. La −3 has different effects on mitochondria from Neurospora , Jerusalem artichoke tubers and Arum spadices. The results indicate that the fluorescence of 9‐aminoacridine can be used to monitor binding sites on biological membranes.