Adenovirus type 2 hexon polypeptides have been traced from their synthesis on cytoplasmic polyribosomes through their incorporation into whole virions. Analysis of the methionine-containing tryptic peptides of hexon and penton revealed that they had no methionine-containing peptides in common, eliminating the possibility of a precursor-product relationship. Nascent hexon peptides were found on the cytoplasmic polysomes and required 3-4 min to be synthesized and released from the ribosomes. Between 80% and 90% of the hexon peptides were assembled into complete capsomeres within an additional 3-4 min of their release from the ribosome, while the remaining 10-20% were assembled more slowly. The penton base and fiber peptides were synthesized and released from their ribosomal site of synthesis in approximately 2 min. Although there was an initial rapid association of 24% of the fiber and penton base peptides into pentons, many hours were required for the completion of this assembly. Studies on the morphogenesis of complete virions showed that radioactive core peptides began to appear in virions within 15 min of their synthesis, when radioactive hexon peptides were still undetectable in assembled virus.
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