Protein Synthesis by Isolated <em>Acetabulavia</em> Chloroplasts.

Isolated chloroplasts of Acetabularia incorporate radioactive amino acids into more than 30 polypeptides in the light, including the apoprotein of the P700-chlorophyll a protein complex, the reaction centre core of photo- system I [Biochim. Biophys. Acta, 609, 107–120 (1980)]. In this paper it is shown that the apoproteins of the two minor chlorophyll a complexes, thought to be part of photosystem II reaction centre core, are also syn- thesized by isolated chloroplasts. Furthermore, they are integrated correctly into the thylakoid membrane in the absence of any cytoplasmic contribution, such that they can be isolated as chlorophyll-protein complexes indistinguishable from those already in the membrane. In contrast, the minor chlorophyll a + b complex ‘CP 29’ [Camm, E. L. and Green, B. R. (1980) Plant Physiol. 66, 428–432] and its dimers are not synthesized by isolated chloroplasts. In this they resemble the other chlorophyll a + b complex, the light-harvesting complex (LHC). It may be significant that the LHC, which is not essential for photosynthetic activity, is under nuclear control, while the reaction centre polypeptides, cytochrome b₅₅₉, and cytochrome f, are synthesized on chloroplast ribosomes. [ABSTRACT FROM AUTHOR]