Coupling of chlorophyll metabolism with submembrane chloroplast particles, isolated with digitonin and gel electrophoresis.

An unusual set of submembrane particles is obtained from digitonintreated barley chloroplasts as five gel-electrophoretic zones. Four of them are photochemically active, whereas the most mobile fifth zone has essential traits of the light-harvesting complexes. All of the particles contain the well-known chlorophyll-protein complexes and represent an intermediate level of membrane organization. When isolated from plants fed delta-aminolevulinate in the dark, the fifth zone is characterized by a high level of protochlorophyllide, which is also present to a lesser extent in all the other zones. When [(14)C]aminolevulinate was fed in the dark, followed by exposing the plants to light, the same pattern of the distribution was observed for [(14)C]chlorophyll a. Thus, particles of all the types are involved in chlorophyll formation and the fifth zone is the most distinct in this respect. Its material seems to originate from the most intensely developing areas of the metabolically heterogeneous chloroplast membrane system.