NUCLEOIDS OF PEA-CHLOROPLASTS - MICROSCOPIC AND CHEMICAL CHARACTERIZATION - OCCURRENCE OF HISTONE-LIKE PROTEINS

The chloroplast genome is highly condensed and packed into discrete st ructures called ''nucleoids''. Each pea chloroplast contains 16-20 sph erical nucleoids randomly located in the matrix of organelle. Nucleoid s are shown to contain DNA, RNA and proteins (1:0.62:2.3). Approximate ly 30 polypeptides (mel. masses 94 to 12 kD) have been found in nucleo ids. Chloroplast DNA is associated with acidic as well as basic protei ns, two of which are electrophoretically similar to histones H2A+H2B a nd H3 of pea cell nuclei. Amino acid composition of these proteins dem onstrates high similarity with ''HU'' proteins of E.coli.