molecular detection of proteolytic activity of human parechovirus 2a protein by gene expression

parechoviruses form one of the nine genera in the picornaviridae family, and include two human pathogens: human parechovirus type1 and 2 (hpev1 and hpev2). the genome of picornaviruses encodes a single polyprotein, which undergoes a cleavage cascade performed by virus encoded proteases to give the final virus proteins. the primary cleavage occurs by 2a protein and this step is critical for viral life cycle. recent sequence analysis suggests that hpev1 is distinct from other picornaviruses and lacks the motifs believed to be involved in the protease function of 2a. the aim of this study was to analyze proteolytic activity of 2a protein in hpev1. for this purpose we made several recombinant plasmids contain 2a region of parechovirus type1 genome and expressed in prokaryotic and in vitro systems under t7 promoter. analyzing the expression products by sds-page revealed just a large single band (90 kda), the same size as primary translation product. whereas with plasmids include 3c gene several small bands were observed, indicating that processing had occurred. in conclusion: the results of this work show that human parechovirus type1 has a processing strategy different from the other members of picornaviruses and in this virus, as in hepatovirus, 2a protein does not have a protease function.