Some Requirements for the Insertion of the Precursor of Apoproteins of Lemna Light-Harvesting Complex II into Barley Thylakoids

Abstract

The light-harvesting complex of photosystem II (LHC 11 β) has the chlorophyll a/b-binding proteins (LHCPs) as its major component. The LHCPs are encoded in the nucleus and are synthesized on cytoplasmic ribosomes as a soluble, higher molecular weight precursor form(s) (pLHCP) (1). The pLHCP is imported into the chloroplasts and then is processed to its mature form (1). In our previous studies we showed that when barley etiochloroplasts were incubated with Lemna pLHCP, synthesized in vitro, both the precursor and the processed, mature polypeptides are found in the thylakoids and also in the LHC II β (2). In the present studies we show that when the precursor is incubated with the isolated barley thylakoids it associates with them; however, some stromal factor is apparently necessary for the integration of precursor into the thyalkoids.