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 nmol mm 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.