Structural polypeptides of adenovirus type 16 incomplete particles

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Abstract
The polypeptides of adenovirus type 16 incomplete particles, with average buoyant densities of CsCl of 1.33, 1.318, 1.305, and 1.299 g/cm3 and DNA content of less than 1 U genome size, were compared with the polypeptides of the complete virion (density, 1.344 g/cm3, and 22 x 10(6) daltons of DNA) and late polypeptides in infected cells by using sodium dodecyl sulfate-gel electrophoresis. In agreement with other serotypes studied (types 2 and 3), the light particles lack polypeptides V, VI, and VII. In adenovirus type 16, eight other major polypeptides are found, with apparent molecular weights of 59,000 (59K), 46K, 31K, 30K, 28K, 27K, 26K, and 19K. The 30K to 31K and 27K to 28K polypeptides are phosphorylated. The 27K and 19K polypeptides are precursors, whereas the 31K, 30K, and 26K polypeptides are chase products in the cell, as are polypeptides VI, VII, and VIII. The 26K polypeptide is proposed to be an intermediate in processing since it disappears from the young virions upon chasing. Although chase products, the 31K and 30K polypeptides are only associated with particles having buoyant density lower than 1.318 g/cm3. Polypeptides V and VII are only present in particles containing more than one quarter of the genome. No trace of cell histones could be detected in the purified incomplete particles. A major constituent of the incomplete particles, the 46K polypeptide, was rapidly labeled in the cell, and loss of radioactivity from this band was detectable only after 7 to 18 h of chase.