Cytochromes and prenylquinones in preparations of cytoplasmic and thylakoid membranes from the cyanobacterium (blue-green alga) Anacystis nidulans

The cytochrome and prenylquinone compositions were compared for cytoplasmic membranes and thylakoid membranes from the cyanobacterium (blue-green alga) Anacystis nidulans. Reduced-minus-oxidized difference absorption spectra at ?196°C indicated that the thylakoid membranes contained photosynthetic cytochromes such as cytochrome ?, cytochrome b-559 and cytochrome b₆, while cytochromes c-549 and c-552 were detected spectrophotometrically only after their release by sonic oscillation. The cytoplasmic membrane preparation contained one or two low-potential cytochrome(s) with α-band maxima at 553 and 559 nm at ?196°C, which differed from the cytochromes in the thylakoid membranes. A cytochrome specific to the cytoplasmic membranes was also found by heme-staining after lithium dodecyl sulfate-polyacrylamide gel electrophoresis. Both types of membranes contained the three prenylquinones plastoquinone-9, phylloquinone and 5′-monohydroxyphylloquinone, but in different proportions.