STRUCTURE OF TOBACCO NECROSIS VIRUS .I. PROTEIN SUBUNIT AND NATURE OF NUCLEIC ACID

The Urbana isolate of the tobacco necrosis virus (TNV) has been grown in and purified from Nicotiana tabacum var. Xanthi n.c. without detectable contamination by its satellite (STNV). The isolate, however, was capable of supporting the multiplication of the STNV. The RNA content of TNV was 18.7%. The sedimentation coefficients of the TNV and its RNA were 120 S and 27 S, respectively. The molecular weight of the TNV RNA, calculated from its sedimentation coefficient, was 1.57 × 106. The base composition of the TNV RNA was: 23.4% G, 28.8% A, 23.5% C, 24.3% U. The viral capsid has been shown by polyacrylamide gel electrophoresis to consist of one protein species. The minimum molecular weight of the protein subunit calculated from amino acid analyses assuming one residue of histidine per mole protein is 33,300. The molecular weight of the protein subunit as determined by electrophoresis in sodium dodecyl sulfate-containing polyacrylamide gels in the presence of markers of known molecular weight is in precise agreement with this value. © 1969.