Organization of the avian adenovirus genome and the structure of its endopeptidase.

In the search for the endopeptidase gene, short segments of genomic DNA were sequenced from the avian adenovirus type 1 (CELO) HindIII C and G fragments. On the basis of homology of the translated segments to Ad2 proteins, the genes for hexon, endopeptidase, DNA-binding protein, and 100K protein were mapped in that order between map units 41 and 63. The endopeptidase gene was encoded within a 900 nucleotide segment extending leftward from the EcoRI site at coordinate 50. The predicted Aavl endopeptidase consists of 206 residues of which 66% are similar to the sequence of the human Ad2 enzyme. Alignment of the known endopeptidase sequences identifies a single conserved histidine (H54) and two conserved cysteine residues (C104, C122) as likely candidates for the catalytic site of this thiol proteinase.