Altered chloroplast ribosomal proteins in a yellow mutant of Chlamydomonas reinhardii.

Ribosomes and ribosomal proteins from wild-type and a yellow mutant of Chlamydomonas reinhardii were analysed and compared by two-dimensional gel electrophoresis. Mixothrophycally grown yellow-27 mutant differs from wild-type cells in lowered chlorophyll content and grana formation of the chloroplast. Analytical ultracentrifuge analyses of cell extracts show a reduced amount of free 70S ribosomes and increased level of 50S subunits in the mutant cells. Similar results were obtained by electronmicroscopical method. Two-dimensional gel electrophoresis shows alterations in protein composition of 70S ribosomes of the mutant. Two proteins of 70S ribosomes have been altered. One of them with high molecular weight is practically absent while there is an additional, intensively stained spot in the mutant. Since the mutation is inherited in a non-Mendelian manner it is possible that the protein alterations in 70S ribosome are localized in the chloroplast DNA.