IDENTIFICATION OF RESIDUES CRITICAL FOR THE HUMAN CORONAVIRUS 229E RECEPTOR FUNCTION OF HUMAN AMINOPEPTIDASE N

Aminopeptidase N (APN) is the major cell surface receptor for group 1 coronaviruses. In this study, we have isolated and characterized a fel ine APN cDNA and shown that the transfection of human embryonic kidney cells with this cDNA renders them susceptible to infection with the f eline coronavirus feline infectious peritonitis virus, the human coron avirus (HCV) 229E and the porcine coronavirus porcine transmissible ga stroenteritis virus. By using chimeric APN genes, assembled from porci ne and feline sequences, we have shown that, analogously to the human APN protein, a region within the amino-terminal part of the feline APN protein (encompassing amino acids 132-295) is essential for its HCV 2 29E receptor function. Furthermore, by comparing the relevant feline, human and porcine APN sequences, we were able to identify a hypervaria ble stretch of eight amino acids that are more closely related in the feline and human APN proteins than in the porcine APN molecule. Using PCR-directed mutagenesis, we converted this stretch of amino acids wit hin the porcine APN molecule to the corresponding residues of the huma n APN molecule. These changes were sufficient to convert porcine APN i nto a functional receptor for HCV 229E and thus define a small number of residues that are critically important for the HCV 229E receptor fu nction of human APN.