DNA Sequence of the Adenovirus Type 41 Hexon Gene and Predicted Structure of the Protein

The gene for the major capsid protein (hexon) of human adenovirus type 41 (Ad41) has been isolated and the complete DNA sequence determined. Comparison of the predicted amino acid sequence with hexons from human Ad2 and Ad5 and bovine adenovirus type 3 reveals regions of high homology at the N and C termini separated by a central region of low homology. Fitting of the Ad41 hexon sequence to the known three-dimensional structure of the Ad2 hexon demonstrates that both hexons have a common architecture. Regions of the hexon which in the trimer constitute the pseudohexagonal base are highly conserved, with the major amino acid changes concentrated in the domains forming the triangular towers which represent the surface of the capsid. Changes in the Ad41 towers therefore permit the virus to present a unique surface to the environment while conservation of residues in the base maintains the integrity of hexon-hexon contacts. A striking difference is the absence in the Ad41 sequence of 32 amino acids which are present in the Ad2 sequence. In Ad2 this region is highly charged and may be responsible for pH-induced conformational changes within the virus capsid. The DNA sequence in the region surrounding the Ad41 hexon gene was also determined and revealed an open reading frame which appeared to code for the homologue of the Ad2-coded endoprotease. Comparison of the predicted amino acid sequences of the Ad41 and Ad2 proteins revealed a high degree of homology suggesting that this protein may have an important role in the infectious cycle of the virus.