Einbau von Uridin und Orots�ure in plastid�re ribosomale RNA von Chlorella nach Antibiotica-Behandlung
✍ Scribed by Galling, Gottfried
- Publisher
- Springer-Verlag
- Year
- 1972
- Weight
- 840 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0003-9276
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✦ Synopsis
Incorporation of Uridine and of Orotatc into Chloroplast Ribosome RNA of ChloreUa after Treatment with Antibiotics Summary. Normal grown cells of Chlorella 19yrenoidosa incorporate uridine exclusively into chloroplast ribosomal RNA after short time labeling. With sucrose gradient separation, labeled ribosomal particles of 70 S, 50 S and 30 S can be shown. This labeling is prevented by rifampin in low concentrations after a few minutes. At the same concentration of the antibiotic and also with 10-fold higher concentration, no effect on heterotrophie cell growth is observed. This indicates clearly that mitochondria cannot be influenced by rifampin. Chloramphenicol also inhibits the formation of uridine labeled ribosomal particles of 70 S, 50 S and 30 S. In the presence of this antibiotic, some labeled ribosomal RNA is formed. Also the effect of chloramphenicol can be shown after short incubation periods. Cyeloheximide treatment of the cells within 30 and 60 min and up to the 10-fold concentration of protein synthesis inhibition (Morris, 1967) results in no effect on labeling of ribosomal RNA and of ribosomal particles in Chlorella with uridine. Only after prolonged treatment of the cells with eycloheximide is some effect on uridine incorporation observed.
The comparison of the incorporation patterns of 6-(14C)-orotate, (6-14C)-uridine and 5-(3H)-uridine into nucleic acids in the presence of rifampin, chloramphenicol and cyeloheximide shows some similarities. After 60 min incubation with the precursors, the incorporation is reduced by all three antibiotics. In rifampin treated cells, orotate and both uridines are preferentially incorporated into DNA. With chloramphenicol, the relative incorporation of orotate and of uridine into the 5 S and the 16 S RNA is higher as compared with the 23 S RNA. Cyeloheximide results in an increase in the relative incorporation of orotate as well of uridine into DNA. The similarities of the effects of the three antibiotics indicate that the preferential incorporation of uridine into chloroplast ribosomes of Chlordla is not due to a compartmentation of the uridine-UMP-pathway.
Zusammen]assung. Chlorella pyrenoidosa inkorporiert unter normalen Anzuehtbedingungen kurzfristig angebotenes Uridin fast aussehlie~lieh in plastid~re ribo-* Z. Zt. Centre de Biochimie et de Biologie l~ol6culaire, C.N.R.S., F-13 Marseille, Frankreieh.