<p> Monomeric ribosomes and very few subunits are found in mammalian cells and because subunits are required for initiation of protein biosynthesis in both mammalian and bacterial systems, this implies that the dissociation step in the ribosome cycle does not occur spontaneously. Our attention was drawn to the possibility that the monomeric ribosomes in mammalian cells could complex with a dissociation factor. This factor would perhaps be present in the cell in limited supply and would, therefore have to recycle in the course of initiation, from a completed initiation complex to another free ribosome. An assay was set up whereby the existence of a dissociation factor in a subcellular fraction of rat liver could be determined. The perfecting of the assay system for the dissociation factor yielded much information on the ionic concentration necessary for both ribosome and subunit stability. The factor was found to be present in the fraction containing the "native" subunits. This is identical to the situation which exists in E. coli. The factor is capable of dissociating rat liver monomeric ribosomes into 60S and 40S subunits. The factor was found to act on ribosomes freed of both messenger RNA and nascent protein.</p> <p> Purification of the crude dissociation factor preparation was achieved by obtaining at 4°C the 35-65% ammonium sulphate fraction. Purification was also achieved by means of an incubation of the preparation at 40°C for 30 minutes followed by a centrifugation to remove precipitated protein.</p> <p> The DF was determined to have a molecular weight in excess of 85,000 by column chromatography.</p> / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/17954 |
| Date | 09 1900 |
| Creators | Hey, William Charles |
| Contributors | Lawford, G.R., Biochemistry |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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