CHARACTERIZATION OF ADENOVIRUS PROTEIN-IX

Protein IX from adenovirus type 2 was purified by 2 methods, one from groups of 9 hexons obtained by disrupting purified virus by heating in the presence of deoxycholate, and the other by a previously published method. The purified protein was used to obtain a monospecific antiserum. Protein IX possessed both sub-group- and type-specific antigenic determinants which were apparently accessible within the groups of 9 hexons. Approximately 15 molecules of IX were found per group of 9 hexons; from based on symmetry it seemed possible that IX was located at the corner to edge contacts between hexons in the icosahedron. The protein in infected [human] cells possessed approximately neutral charge as determined by immunoelectrophoresis. This was consistent with the amino acid composition, which showed it to be rich in serine, alanine and leucine with about half of its glutamic and aspartic acid residues amidified, and the isoelectric point of 6.0, as determined by 2-dimensional gel analysis. No free N[amino]-terminal amino acid was detectable. A unique tryptophan residue is located at around position 70 from the blocked N-terminus, on the basis of chemical cleavage by BNPS-skatole. Based on 1 tryptophan residue a total of 107 amino acids and a MW of 11,200 was deduced. Analysis of 35S-methionine-labeled infected cell extracts in a 2-dimensional gel system showed that the synthesis of polypeptide IX could be detected early in infection, i.e., in the presence of an inhibitor of DNA synthesis.