SDS‐acrylamide gel electrophoresis and its application to the proteins of poliovirus‐and adenovirus‐infected human cells

Sensitive techniques for acrylamide gel electrophoretic analysis have been applied to animal virus systems and have proven generally useful. Estimates of the number of kinds, molecular weights and number of molecules of proteins in almost any biological sample have been made with ease. As applied to the poliovirus‐HeLa cell system they reveal four major proteins in the virion and at least ten additional proteins in the infected cell. Some of the intracellular and particulate proteins undergo cleavage reactions following a unique translation in which the genome is apparently translated in toto as one large polypeptide of molecular weight greater than 200,000 daltons. The splits occur at three levels: (a) during synthesis; (b) at intermediate stages; and (c) co‐incident with maturation. In vitro studies on protein synthesis, RNA synthesis and virus assembly have substantiated and extended the in vivo observations. The structure of the adenovirion has been established in detail. Hexon, penton base, fiber and core polypeptides and certain relevant subviral structures have been identified. Nearly all of the proteins synthesized in the infected cells after 20 hours are viral. The major structural antigens (hexon and penton) predominate and are made in 10 to 50 fold excess but the internal core polypeptides are not produced in great excess. Studies on the synthesis of polypeptides and their assembly into morphological subunits and virions show that hexon and penton polypeptides are made in about four and two minutes respectively on cytoplasmic polyribosomes, that morphological subunits are formed within five minutes of synthesis of protein, and that there is a delay of greater than one half hour for entry of hexons into virions.