THE INCORPORATION OF RADIOACTIVE IRON-59 INTO TOBACCO MOSAIC VIRUS AND YEAST NUCLEOPROTEIN

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4774097

Fook Eng, L

The significance and origin of the iron associated with tobacco mosaic virus first reponted by Loring and Waritz, Science, 125: 648(1957) were further investigated with a radioactive tracer study. It was shown that iron-59 was incorporated in much larger amounts in the isolated virus under conditions of rapid synthesis in newly-infected Turkish tobacco plants than under conditions prevailing in the plants of the same age that had been infected several weeks. Adsorption experiments showed that all the iron associated with the virus could not be attributed to adsorption. The observations that virus prepared in its most native state contained primarily calcium and magnesium and small amounts of other metals such as iron and manganese and that the iron content of the virus could be decreased considerably if potassium phosphate were added to the infected juice before isolation of the virus were confirmed. Extensive treatment of native virus with sodium versene decreased the iron content of the virus to no more than five atoms per molecule (using a MW of 40 x 10/sup 6/) without changing its infectivity. Flame photometric analysis of virus that was treated extensively with versene showed that it was essentially in the sodium form. The incorporation of iron59 into tobacco mosaic virus lesions of N. glutinosa leaves was studied by radioautography and iron radioactivity comparisons between comparable areas containing and areas free from local lesions. It was found that the areas with lesions contained more radioactivity than areas free from lesions. Nucleic acid was prepared from the radioactive virus by a phsnol extraction procedure. It was found that the majority of the iron associated with the virus was er sedimenting nucleate fraction was obtained by ultracentrifugation which contained about four times as much radioactivity as the slower sedimenting nucleate fractions. It was concluded that while iron is not essential for maintaining the infectivity of the virus, it may function in the secondary structure of the virus molecule. The iron contents of the yeast ribosomes and ribonucleic acid were determined by a radioactive tracer stady. The ribosomes were prepared by a modified procedure of Chao and Sehachman, (Arch. Biochem. Biophys., 61: 220(1858)) from yeast cells cultured in synthetic medium contnining iron-59. The total iron content of the medium was determinsd by chemical analysis and its spscific radioactivity per unit of total iron established from the radioactivity of a known aliquot. By assuming that the iron found subsequently in the various fractions had the same spscific activity as that of the medium, it was possible to estimate total iron content from radioactivity measurements. Relatively constant iron recovery in the ribosome fractions indicated that iron was distributed in fairly constent proportions between the ribosomes and the rest of the cell components. Some physical and chemical propenties of the ribosomal panticles were determined. Repeated cycles of purification caused a progressive decrease in the ratio of iron to phosphorus. The average ratio of iron to phosphorus was 10.9, 10.3, and 7.2 mg Fe ger g P for two-, three-, and four-cycle ribosomes while one five-cycle sample contained 7.4 and one seven-cycle preparation contained 5.1 mg Fe per g P. Ribosomal nucleic acid was prepared by the detergent and phenol methods under various conditions. As in the case of tobacco mosaic virus treated with phenol, the majority of the iron in the ribosomal particles was removed with the protein in the phenol extract. A possible function of the iron associated with the ribosomes is discussed. (Dissertation Abstr., 23: No. 3, 1962)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-17-001229
• OSTI ID: 4774097
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ADSORPTION
AGE
BIOLOGY AND MEDICINE
CALCIUM
CENTRIFUGATION
CYTOLOGY
DETERGENTS
DISEASES
EDTA
INFECTIONS
IRON
IRON 59
MAGNESIUM
MANGANESE
MEASURED VALUES
MEDICINE
MOLECULES
NICOTIANA
NUCLEIC ACIDS
PHENOLS
PHOSPHORUS
PHOTOMETRY
PLANT CELLS
PLANTS
POTASSIUM PHOSPHATES
PREPARATION
PROTEINS
QUALITATIVE ANALYSIS
QUANTITY RATIO
RADIOACTIVITY
RADIOAUTOGRAPHY
RECOVERY
RIBONUCLEIC ACID
RIBOSOMES
SEPARATION PROCESSES
SODIUM COMPOUNDS
SUSPENSIONS
TOBACCO
TOBACCO MOSAIC
TRACER TECHNIQUES
VIRUSES
YEASTS