Isolation and characterization of an extremely basic protein from adenovirus type 5.

By starch-gel electrophoresis and a staining method that is highly sensitive for argininyl residues, adenovirus type 5 was found to contain two minor basic polypeptides of extreme cathodic mobility in addition to the two known core proteins. The fastest-migrating polypeptide, named mu protein, and the second fastest polypeptide are found in adenovirions and virus-infected KB cells but not in top components or in uninfected cells. The top components and infected cells contain an additional basic polypeptide, presumably P-VII, that migrates slightly slower than polypeptide VII. None of the basic polypeptides of adenovirions was electrophoretically identical to the host histone. The basic proteins of adenovirions were purified by urea phosphocellulose column chromatography and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two minor basic core proteins, mu and another component, have similar mobilities in sodium dodecyl sulfate-polyacrylamide gels as a complex of polypeptides X-XII. After further purification on a Sephadex G-75 column, the mu protein was found to have a molecular weight of about 4,000. Amino acid analysis showed that the mu protein lacks tryptophan and 69% of the total amino acid residues are basic, that is, 54% arginine, 13% histidine, and 2% lysine. Only eight amino acids seem to contribute to make the mu polypeptide. There are 125 copies of the mu polypeptide per 1,000 copies of polypeptide VII in a virion.