Chloroplast Import of Light-Harvesting Chlorophyll a/b-Proteins with Different Amino Termini and Transit Peptides.

We have previously isolated and sequenced two genes encoding light-harvesting chlorophyll a/b-proteins (LHCP) from Lemna gibba. One of these, AB30, encodes a protein that is highly homologous to LHCP sequences reported from other species, but the second, AB19, encodes a protein that has a transit peptide and first 12 amino-terminal residues of the mature protein that are substantially different. Despite these differences, we can demonstrate that AB19 encoded protein synthesized in vitro can be imported into isolated chloroplasts, and we provide evidence that at least some of the imported molecules are assembled into the light-harvesting complex of photosystem II. Thus, our results are consistent with the possibility that there are two functional forms of LHCP.