Expression in baculovirus-infected insect cells allows sufficient production of G-protein coupled receptor for structural studies. An important drawback of this expression system comes from the presence of unprocessed and biologically inactive receptors that have to be eliminated during receptor purification steps. We show that viral particles released from Sf9 cells infected with a recombinant baculovirus coding for the human beta 2-adrenergic receptor (beta 2AR) cDNA contain glycosylated and biologically active beta 2AR. In addition, post-translational modifications known to modulate receptor activity were found to occur in these particles.