Comparison of Two Serologically Distinct Ribonucleic Acid Bacteriophages II. Properties of the Nucleic Acids and Coat Proteins

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Abstract
Overby , L. R. (University of Illinois, Urbana), G. H. Barlow, R. H. Doi, Monique Jacob, and S. Spiegelman . Comparison of two serologically distinct ribonucleic acid bacteriophages. II. Properties of the nucleic acids and coat proteins. J. Bacteriol. 92: 739–745. 1966.—The ribonucleic acid (RNA) molecules and coat proteins of two RNA coliphages, MS-2 and Qβ, have been characterized. MS-2 RNA shows an S 20,w of 25.8 and a molecular weight by light scattering of 10 6 . The corresponding parameters for Qβ-RNA were 28.9 and 0.9 × 10 6 . A difference in base composition was reflected in the adenine-uracil ratio, which was 0.95 for MS-2 and 0.75 for Qβ. The two RNA preparations are readily separated by chromatography on columns of methylated albumin. Both gave identical bouyant densities in cesium sulfate of 1.64 g/ml. The coat protein subunits were of similar molecular weights: 15,500 (Qβ) and 14,000 (MS-2). They differed, however, in that the Qβ-protein lacked tryptophan and histidine, whereas the MS-2 protein lacked only histidine.