Fig. 5.

Electron spin resonance spectroscopy (ESR) spectra of RAS2^gly18val19 yeast cells. The yeast “oncogenic” mutation RAS2^{gly18, val19} produces high levels of superoxide even in the absence of the mitochondrial respiratory chain. Therefore, the authors argued that a different source of superoxide must be present and tested all yeast genes for NADPH oxidase activity that show clear homology with the human NADPH oxidases. The figure shows in vivo measurements of the superoxide adducts of the spin trap DEPMPO by electron paramagnetic resonance (EPR). a 5-Diethylphosphono-5-methyl-1-pyrroline N‑oxide (DEPMPO) incubated with RAS2 wild-type cells; no ESR signal is detectable. b DEPMPO incubated with RAS2^ala18,val19 cells; the EPR spectrum clearly shows the presence of the DEPMPO superoxide adduct. c DEPMPO incubated with RAS2^ala18,val19 respiratory deficient rho-zero cells. One sees the same amount of DEPMPO superoxide adduct as in b. (Modified from [84])