FIG 2.

Oxygen consumption activities of the membrane fractions of the quadruple terminal oxidase mutant strains. Bo, Ci, Aa, Cb1, and Cb2 indicate membrane fractions of QXBo, QXCi, QXAaS2, QXCb1, and QXCb2, respectively. A 0.5 mM concentration of NADH (A, B, and C) and a 0.1 mM concentration of TMPD reduced by 5 mM ascorbate (D) were used as electron donors. A 1 mM concentration of KCN (B) or 10 μg/ml antimycin A (C) was added to the reaction mixture to inhibit the heme-copper oxidases or the cytochrome bc₁ complex, respectively. The data are means of results from three independent experiments. Error bars indicate standard deviations from the means.