Partition of Phylloquinone Kx between Digitonin Particles and Chlorophyll-Proteins of Chloroplast Membranes from Nicotiana tabacum

The partition of phylloquinone (vitamin K J, of chlorophylls a and b and of the two main carotenoids, /?-carotene and lutein, in subthylakoid particles (digitonin treatment) and chlorophyll protein complexes (sodium dodecylsulfate polyamide-gel electrophoresis) isolated from tobacco chloroplasts (Nicotiana tabacum L.) is described. 1. The “light particle” fractions (S 90000, S 150000) of digitonin fragmented chloroplasts are enriched in CP I and contain a higher proportion of phylloquinone, chorophyll a and /?-carotene as compared to whole chloroplasts. This is visualized by high values for the ratio a/b (6 -8 ) and for /?-carotene/lutein (1.7) as well as about 3 mol of Kx per 100 mol of total chlorophyll. The “heavy digitonin particle” fraction (10000 x g sediment), in turn, contains a higher proportion of chlorophyll b and lutein, but a lower level of phylloquinone than whole chloroplasts. 2. The chlorophyll a-protein CP I of pigmentsystem I, isolated by preparative gel electro­ phoresis using 0.5% and 4% SDS, is characterized by a stable level of phylloquinone (1 mol Kt per 100 mol of total chlorophyll), high chlorophyll a/b ratios (7 -10 ) and high values for ßcarotene/lutein (~ 6.0). The light-harvesting chlorophyll a/b-protein LHCP of photosystem II (chlorophyll a/b = 1.1 — 1.5, ^-carotene/lutein = < 0.1) contains either low amounts of phylloquinone (0.5% SDS) or only trace amounts of Kj (4% SDS). The free pigment fraction (FP) contains at 0.5% SDS 57% of the total phylloquinone of thylakoid membranes. At 4% SDS the K? amount in the free pigment fraction increases to 84%. 3. The phylloquinone partition studies in digitonin particles and SDS chlorophyll proteins indicate that there exist at least two localization sites for phylloquinone Kj in the photosynthetic membrane. The CP I complex and a second site, presumably near photosystem II (CPa?).