Expression and characterization of soluble human parainfluenza virus type 1 hemagglutinin-neuraminidase glycoprotein

Human parainfluenza virus types 1 (hPIV-1), 2, and 3 represent significant respiratory pathogens for which no antiviral treatment is currently availab le. To characterize the biochemical functions of the hPIV-1 hemagglutinin-n euraminidase (HN) glycoprotein, a potential target for antiviral therapy, w e cloned and expressed a soluble portion of hPIV-1 HN (amino acid residues 137-575), lacking the N-terminal hydrophobic membrane anchorage region, in insect cells using the baculovirus secretion expression system. The express ed HN protein was purified through cation-exchange chromatography followed by metal affinity chromatography, using the 6 x His epitope introduced at t he carboxyl terminus of the recombinant protein. N-terminal amino acid sequ ence analysis of purified HN indicated that the honeybee melittin secretion signal peptide was correctly removed during post-translational processing. Further characterization revealed that the purified HN protein was N-glyco sylated and exhibited neuraminidase activity whose characteristics resemble d those of the native HN protein of hPIV-1 virions. The establishment of th is expression and purification system has allowed us to further explore the biochemical characteristics of paramyxovirus HN and to obtain material tha t could be suitable for X-ray crystallography studies. (C) 2001 Elsevier Sc ience B.V. All rights reserved.