Primary structure of the canine adenovirus PVII protein: functional implications

The DNA sequence of an open reading frame (ORF) corresponding to the canine adenovirus type 1 (Can 1, Utrecht strain) pro-VII (PVII) protein gene was determined. 560 base pairs were sequenced from the upstream end of the HindIII-A genomic fragment. The sequence gives the 33 C-terminal residues of the penton base protein followed by the 132 residue PVII protein, thus conforming to the same order and location of these genes as in Ad2. The authenticity of this putative PVII-ORF was confirmed by N-terminal sequencing of the cleavage product VII isolated from Can1 virions and also by PCR analysis of Can1 DNA from infected cells and from virions. In addition, the sizes of PVII and VII obtained from translation of the sequence and the proteins observed on the gels were also in agreement. The PVII proteins of Can1 and Ad2 share 57% sequence homology, particularly near the N-terminal third of the molecule, including conservation of the consensus proteinase cleavage site at residue 23. The PVII protein has a predicted MW of 14,626 Da, and an pI of 12.48. Though data bank searches for homology were negative, these viral proteins have significant functional and sequence analogy with histone H3.