STUDIES ON NATURE OF DENGUE VIRUSES .4. STRUCTURAL PROTEINS OF TYPE 2 DENGUE VIRUS

The proteins of type 2 dengue virus were labeled by infecting KB cells with virus in the presence of either a mixture of radioactive amino acids or a single radioactive amino acid. Concentrated virus was shown by sucrose gradient centrifugation to contain two major types of hemagglutinating particles designated complete and incomplete virus. Complete virus labeled with mixed amino acids and examined by acrylamide gel electrophoresis contained at least 3 polypeptides: a major slow-moving peak (VSP-3) and two more rapidly moving minor peaks (VSP-1 and VSP-2). Incomplete virus yielded VSP-1 and VSP-3 but lacked VSP-2. By comparing the relative mobilities of Sindbis and dengue structural proteins in acrylamide gel electrophoresis, the following molecular weights were assigned to the dengue proteins: VSP-1, 7700; VSP-2, 13,500; and VSP-3, 59,000. VSP-2 was lysine rich, but incorporation of histidine into this component was not demonstrable. 14C-1-Glucosamine was incorporated into VSP-3 of complete virus. The nonionic detergent Nonidet P40 was used to degrade complete dengue 2 virus into a slowly sedimenting fraction and an RNA-containing core. Gel electrophoresis of these viral components showed that the viral core structure contained VSP-2 and that the slowly sedimenting fraction contained VSP-1 and VSP-3. It is suggested that VSP-3 is a glycoprotein and a major component of the viral envelope, that VSP-2 is the protein moiety of the nucleoprotein core, and that VSP-1 may represent a capsid protein tightly bound to the envelope. © 1969.