Sub-etioplast localization of the enzyme NADPH: protochlorophyllide oxidoreductase.

The membranes from oat etioplasts have been separated by sucrose density gradient centrifugation into a heavy fraction of density 1.20 mg/ml (prolamellar body fraction) and a light fraction of density 1.12 mg/ml (prothylakoid fraction). The light fraction was shown to be enriched in protein, protochlorophyllide and the chloroplast enzyme CF1-ATPase, but to be deficient in saponins. In the electron microscope this fraction appeared as swollen vesicles. In contrast the heavy fraction appeared considerably enriched in crystalline, tubular material and was on analysis found to contain most of the etioplasts' saponin but with reduced protein and pigment. In the same experiments the enzyme NADPH: protochlorophyllide oxidoreductase showed the same distribution pattern as the CF1-ATPase suggesting its location on the prothylakoids.