[Mitochondrial ribosomes of the phytoflagellata Astasia longa].

The physico-chemical properties of ribosomes and rRNA isolated from the mitochondria of the phytoflagellata Astasia longa were studied. It was shown that the mitochondrial ribosomes of A. longa have the sedimentation coefficient of 81S (those of the cytoplasm-82S); upon a decrease of Mg2+ concentration in the medium they dissociate into subparticles with sedimentation coefficients of 60 and 45S. The relative protein content in the mitochondrial ribosomes of A. longa is equal to 42% (rho = 1,60 g/cm3), that of cytoplasmic ribosomes-49%. The molecular weights of mitochondrial rRNA are equal to 1,05 . 10(6) and 0,71 . 10(6) and differ from those for cytoplasmic rRNA (1,32 . 10(6) and 0,94 . 10(6)). It was shown that the GC-content in mitochondrial rRNA is equal to 32,0 mol. %, that in cytoplasmic rRNA-55,9 mol. %. Thus, the mitochondrial ribosomes of A. longa differ in some of their properties from both procaryotic and eucaryotic ribosomes and are probably related to a special type of mitochondrial ribosomes.