Structural proteins of adenoviruses: VIII. Characterization of incomplete particles of adenovirus type 3

Abstract

Incomplete virus particles were isolated from cells infected with adenovirus type 3. More than 30% of the particles recovered at 72 hr after infection were found to be incomplete. Polyacrylamide electrophoresis revealed that incomplete particles were deficient in the two major core polypeptides, but contained enhanced levels of a polypeptide present in complete virions in only minute amounts. The amino acid composition of incomplete particles showed reduced levels of both arginine and alanine compared to virions. These two amino acids are enriched in the core proteins. The main fraction of the incomplete particles contained little, or no, DNA. A small fraction, however, contained DNA which was smaller (about 16 S) than viral DNA, as determined by neutral and alkaline sucrose gradient centrifugation. DNA-DNA hybridizations revealed that the DNA of the incomplete particles was mainly of viral origin. The incomplete particle preparations contained reduced levels of infectivity compared to complete particles. Infectivity may either be caused by aggregation of complete and incomplete particles or by complementation.