HuPAR1 and HuPAR2 chimeras reveal that the C-terminal two-thirds of HuPAR2 is responsible for the increased functionality compared to HuPAR1. eGFP-tagged chimeras (gray oval) were constructed between HuPAR1 (solid black) and HuPAR2 (dashed black). PERV-A 14/220* infection levels were determined for SIRC cells stably expressing each of the chimeric constructs. For purposes of comparison, we arbitrarily set the function of HuPAR1eGFP to 100%. The results indicate that HuPAR2 residues 170–448 contain the sequences responsible for the increased function for PERV-A infection.