Sigma Virus: Growth in Drosophila melanogaster Cell Culture; Purification; Protein Composition and Localization

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Abstract
The growth cycle of sigma virus in D. melanogaster cells was studied: optimal virus production was reached .apprx. 40 h after infection; virus release declined thereafter and then remained approximately constant (carrier state). In the presence of DEAE-dextran during virus adsorption, more cells became infected and sigma virus production was enhanced. Sigma virus was partially purified by a gentle procedure. Five presumptive virus-specific proteins with MW 210K, 68K, 57K, 44K and 25K were observed. The p68 polypeptide was glycosylated and formed the spikes of the virion particles. The nucleocapsid contained a single major protein, p44, and 1 or 2 minor proteins (p210 and probably p57); another protein, p25, was more loosely associated with the nucleocapsid. None of these proteins was found to be phosphorylated.