Identification and characterization of penton base and pVIII protein of egg drop syndrome virus

The nucleotide sequence and location of the penton base and pVIII genes of the egg drop syndrome (EDS) virus an avian adenovirus, were determined. The penton base gene is located at 34.8-38.8 map units. The coding sequence has a length of 1359 nt and encodes a polypeptide of 452 amino acids (aa) with a molecular weight of 51 105 Da. The amino acid sequence shows a homology of 57.3 and 55.3% to the structural protein IH of human adenovirus serotype 2 (HAd2) and fowl adenovirus serotype 1 (FAV1). The penton base protein lacks the integrin binding motifs RGD (Arg-Gly-Asp) and LDV (Leu-Asp-Val). At 65.1-67.3 map units an open reading frame of 753 nucleotides was identified which encodes the structural protein pVIH. It forms a protein of 250 aa with an expected molecular weight of 28 501 Da. Possible protease cleavage sites were identified. Amino acid homologies of 30.8 and 27.7% were found to the HAd2 and FAV1 pVIII genes. Remarkably, the overall amino acid identity with ovine adenovirus pVIII is 52%. The start codons of both genes are shifted leftwards compared with the respective structural elements on the HAd2 or FAV1 genomes which indicates a different genomic organization of the EDS virus.