Nucleotide and amino acid sequence analysis of the porcine adenovirus 23K protein

The genomic location of the viral encoded protease (23K) of porcine adenovirus serotype 3 (PAV3) was determined and the appropriate fragment cloned and sequenced. An open reading frame (ORF) coding for a polypeptide of 203 amino acids and a calculated molecular weight of 23.3 kDa was found. The ORF was situated in a position similar to that of the human adenovirus 23K, that is, between a putative stop codon for the hexon gene and the polyadenylation signal, AATAAA, for the late region 3. Amino acid sequence alignment of the predicted polypeptide with the sequences of the 23K proteins from other mammalian adenoviruses revealed homology of between 50% and 60% for all except the bovine adenovirus type 7, which displayed appreciable variance from the PAV3 putative 23K with an overall sequence homology of approximately 35%. Conserved cysteine, histidine and proline residues believed to be important in the activity of the 23K protein of human adenoviruses were also present in the PAV3 protein. The genomic location and amino acid sequence of the characterised reading frame suggests that this gene is that of the 23K protein of PAV3.