Paramyxovirus fusion (F) protein: a conformational change on cleavage activation.
The fusion (F) protein of the paramyxovirus SV5 promotes both virus-cell and cell-cell fusion. Recently, the atomic structure at 1.4 A of an extremely thermostable six-helix bundle core complex consisting of two heptad repeat regions of the F protein has been described (K. A. Baker, R. E. Dutch, R. A. Lamb, and T. S Jardetsky, Mol. Cell 3, 309-319, 1999). To analyze the conformations of the F protein at various stages of the membrane fusion process and to understand further the role of formation of the six-helix bundle core complex in promotion of membrane fusion, antibodies to peptides corresponding to regions of the F protein were obtained. Major changes in F protein antibody recognition were found after cleavage of the precursor protein F(0) to the fusogenically active disulfide-linked heterodimer, F(1) + F(2), and antibodies directed against the heptad repeat regions recognized only the uncleaved form. A monoclonal antibody directed against the F protein showed increased recognition at the cell surface of the cleaved form of the F protein as compared to uncleaved F protein, again indicating changes in conformation between the uncleaved and cleaved forms of the F protein. Anti-peptide antibodies specific for the heptad repeat regions were unable to precipitate a synthetic protein that consisted of the heptad repeat regions separated only by a small spacer, suggesting that the antibodies are unable to recognize their target regions when the heptad repeats are present in the six-helix bundle core complex. Taken together, these data indicate that the six-helix bundle core complex is not present in the precursor molecule F(0) and that significant conformational changes occur subsequent to cleavage of the F protein.
Dutch
R E
RE
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA.
Hagglund
R N
RN
Nagel
M A
MA
Paterson
R G
RG
Lamb
R A
RA
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D000918:Antibody Specificity; D002460:Cell Line; D003432:Cross-Linking Reagents; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D008561:Membrane Fusion; D008970:Molecular Weight; D009154:Mutation; D010206:Papain / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology; D011233:Precipitin Tests; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins; D020449:Repetitive Sequences, Amino Acid / Q000276:immunology; D018108:Respirovirus; D013388:Succinimides; D014357:Trypsin / Q000378:metabolism; D014760:Viral Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D003432:Cross-Linking Reagents; D004220:Disulfides; D007106:Immune Sera; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D013388:Succinimides; D014760:Viral Fusion Proteins; C035759:3,3'-dithiobis(sulfosuccinimidyl propionate); D014357:Trypsin; D010206:Papain