Thermostability of the human respiratory syncytial virus fusion protein before and after activation: implications for the membrane-fusion mechanism.
Anchorless fusion (F) proteins () of human respiratory syncytial virus (RSV) are seen by electron microscopy as unaggregated cones when the proteolytic cleavage at two furin sites required for membrane-fusion activity is incomplete, but aggregate into rosettes of lollipop-shaped spikes following cleavage. To show that this aggregation occurred by interactions of the fusion peptide, a deletion mutant of lacking the first half of the fusion peptide was generated. This mutant remained unaggregated even after completion of cleavage, supporting the notion that aggregation of involved the fusion peptide. As exposure of the fusion peptide is a key event that occurs after activation of F proteins, the uncleaved and cleaved forms of may represent the pre- and post-active forms of RSV F protein. In an analysis of the structural differences between the two forms, their thermostability before and after proteolytic cleavage was examined. In contrast to other viral proteins involved in membrane fusion (e.g. influenza haemagglutinin), the pre-active (uncleaved) and post-active (cleaved) forms of were equally resistant to heat denaturation, assessed by spectrofluorimetry, circular dichroism or antibody binding. These results are interpreted in terms of the proposed structural changes associated with the process of membrane fusion mediated by RSV F protein.
Ruiz-Argüello
M Begoña
MB
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
Martín
Diana
D
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
Wharton
Steve A
SA
National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Calder
Lesley J
LJ
National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Martín
Steve R
SR
National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Cano
Olga
O
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
Calero
Miguel
M
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
García-Barreno
Blanca
B
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
Skehel
John J
JJ
National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Melero
José A
JA
Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, 28220 Madrid, Spain.
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D005470:Fluorometry; D006358:Hot Temperature; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D018113:Respiratory Syncytial Virus, Human / Q000502:physiology*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000502:physiology*
D014760:Viral Fusion Proteins