Respiratory electron transport in plasma and thylakoid membrane preparations from the cyanobacterium Anacystis nidulans

Plasma and thylakoid membranes were separated and purified from cell‐free extracts of Anacystis nidulans by discontinuous sucrose density gradient centrifugation. Plasma membranes contained less than 0.05% (w/w) chlorophyll per protein. Both plasma and thylakoid membranes oxidized horse heart ferrocytochrome c (10 ± 4 and 3 ± 1 per mg protein, respectively), with strong inhibition by low concentrations of cyanide, sulfide, azide, carbon monoxide, and salicyl aldoxime. The activity was stimulated 125% by 3.5% Tween 80 and totally suppressed by 100 mM NaCl. Oxidized cytochrome c was reduced by both types of membranes in the presence of NAD(P)H. The results indicate the occurrence of a respiratory chain including cytochrome‐c oxidase in both plasma and thylakoid membranes of A. nidulans.