title: Potential electrostatic interactions in multiple regions affect human metapneumovirus F-mediated membrane fusion.
abstract: The recently identified human metapneumovirus (HMPV) is a worldwide respiratory virus affecting all age groups and causing pneumonia and bronchiolitis in severe cases. Despite its clinical significance, no specific antiviral agents have been approved for treatment of HMPV infection. Unlike the case for most paramyxoviruses, the fusion proteins (F) of a number of strains, including the clinical isolate CAN97-83, can be triggered by low pH. We recently reported that residue H435 in the HRB linker domain acts as a pH sensor for HMPV CAN97-83 F, likely through electrostatic repulsion forces between a protonated H435 and its surrounding basic residues, K295, R396, and K438, at low pH. Through site-directed mutagenesis, we demonstrated that a positive charge at position 435 is required but not sufficient for F-mediated membrane fusion. Arginine or lysine substitution at position 435 resulted in a hyperfusogenic F protein, while replacement with aspartate or glutamate abolished fusion activity. Studies with recombinant viruses carrying mutations in this region confirmed its importance. Furthermore, a second region within the F(2) domain identified as being rich in charged residues was found to modulate fusion activity of HMPV F. Loss of charge at residues E51, D54, and E56 altered local folding and overall stability of the F protein, with dramatic consequences for fusion activity. As a whole, these studies implicate charged residues and potential electrostatic interactions in function, pH sensing, and overall stability of HMPV F.
authors: Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, USA.
authors: Andres
authors: A
authors: Chang
authors: Brent A
authors: BA
authors: Hackett
authors: Christine C
authors: CC
authors: Winter
authors: Ursula J
authors: UJ
authors: Buchholz
authors: Rebecca Ellis
authors: RE
authors: Dutch
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology*; D029121:Metapneumovirus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
chemical_list: D011994:Recombinant Proteins; D014760:Viral Fusion Proteins