This dissertation is divided into three parts.
The first section is concerned with protein synthesis in cellfreesystems from reticulocytes. The sub-cellular reticulocyte fractions,reagents, etc. have been examined for the presence of traces of ribonuclease,using. an assay based upon the loss of infectivity of RNAfran bacteriophage MS2. This assay is sensitive to 5 x 10-7 γ RNase/ml.In addition, the loss of synthetic capacity of an 80S ribosome on dissociationhas been studied, and can be attributed to loss of messengerRNA when the monomer is separated into subunits. The presence ofribonuclease has been shown to be a major cause of polyribosome disintegrationduring cell-free protein synthesis.
The second section concerns the changes in ribosomes and polyribosomeswhich occur during the maturation of a reticulocyte into anerythrocyte. With increasing age, the cells lose a large proportion ofthe ribonucleoprotein, but the percentage of ribosomes present as polyribosomesis only slightly altered. The loss of hemoglobin synthesison maturation is probably due to both the loss of total ribosomesand to the lessened specific activity of the polyribosomes.
The third section contains analytical ultracentrifugation dataon 80S ribosomes, polyribosomes, and ribosomal RNA from reticulocytes.The 60s and 40s subunits, obtained by dissociation of the 80s particlewith inorganic pyrophosphate, were also studied. The RNA from reticulocyteribosomes has been examined under a variety of denaturing conditions,including dimethyl sulfoxide treatment, formaldehyde reaction and thermaldenaturation. From these studies we can conclude that the 28S and16S RNA's are single polynucleotide chains and are not made up ofsmaller RNA subunits hydrogen-bonded together.
