A dual-functional paramyxovirus F protein regulatory switch segment: activation and membrane fusion.
Many viral fusion-mediating glycoproteins couple alpha-helical bundle formation to membrane merger, but have different methods for fusion activation. To study paramyxovirus-mediated fusion, we mutated the SV5 fusion (F) protein at conserved residues L447 and I449, which are adjacent to heptad repeat (HR) B and bind to a prominent cavity in the HRA trimeric coiled coil in the fusogenic six-helix bundle (6HB) structure. These analyses on residues L447 and I449, both in intact F protein and in 6HB, suggest a metamorphic region around these residues with dual structural roles. Mutation of L447 and I449 to aliphatic residues destabilizes the 6HB structure and attenuates fusion activity. Mutation of L447 and I449 to aromatic residues also destabilizes the 6HB structure despite promoting hyperactive fusion, indicating that 6HB stability alone does not dictate fusogenicity. Thus, residues L447 and I449 adjacent to HRB in paramyxovirus F have distinct roles in fusion activation and 6HB formation, suggesting this region is involved in a conformational switch.
Howard Hughes Medical Institute, Evanston, IL 60208, USA.
Charles J
CJ
Russell
Karen L
KL
Kantor
Theodore S
TS
Jardetzky
Robert A
RA
Lamb
D000595:Amino Acid Sequence; D000818:Animals; D002522:Chlorocebus aethiops; D015707:HN Protein / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D020128:Inhibitory Concentration 50; D008561:Membrane Fusion; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025203:Phosphofructokinase-1, Muscle Type; D025221:Phosphofructokinases; D017354:Point Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D018108:Respirovirus; D017386:Sequence Homology, Amino Acid; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D015707:HN Protein; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; D014760:Viral Fusion Proteins; D025221:Phosphofructokinases; D025203:Phosphofructokinase-1, Muscle Type; C026043:PFKM protein, human