Electron transport in a Park-Williams strain of Corynebacterium diphtheriae

Abstract

The electron-transport mechanism was examined in the "particulate" and "supernatant" fractions of disintegrated cells of a Park-Williams strain of C. diphtheriae. Succinate-oxidase activity was found mainly in the "particulate" fraction, and reduced nicotinamide adenine dinucleotide (NADH2) oxidase mainly in the "supernatant", which was devoid of cytocnromes and menaqulnone. The sum of the activities of particles and supernatant fractions, with respect to both succlnate oxidase and NADH2 oxidase, was substantially less th;.n that of the crude cell extract from which they were obtained. Full activity was restored on recombining "particles" and "supernatant". The characteristics of this reassembled system were investigated. The strain of organism (Cn 2000) examined contained cytochromes corresponding spectroscopically to "a", "b" and "c" types. All three were reduced by succinate, lactate or NADH2; but a portion of the cytochrome-b, susceptible to reduction by dithionite, could not be reduced by the substrates. Triton X-100 inhibits oxidation of. succinate by particulate fraction; on adding succinate, the reduction of cytochrome-b is not affected but that of cytochromes-a and -c is delayed. Irradiation at 360 m[mu] completely destroys menaquinone in the particle fraction. Succinate oxidation is severely decreased; succinate dehydrogenase and NADH2 oxidation are little affected. Certain menaquinones will restore succinate oxidation in the irradiated material. On adding succinate to irradiated particulate material cytochrome-b is partially reduced at once, but reduction of cyto-chromes-a and -c is much delayed. A portion of the cytochrome-b remains not reduced, but reduction occurs rapidly on the addition of menaquinone (MK-2).