Second-site revertants of a Semliki Forest virus fusion-block mutation reveal the dynamics of a class II membrane fusion protein.
The alphavirus Semliki Forest virus (SFV) infects cells through low-pH-induced membrane fusion mediated by the E1 protein, a class II virus membrane fusion protein. During fusion, E1 inserts into target membranes via its hydrophobic fusion loop and refolds to form a stable E1 homotrimer. Mutation of a highly conserved histidine (the H230A mutation) within a loop adjacent to the fusion loop was previously shown to block SFV fusion and infection, although the mutant E1 protein still inserts into target membranes and forms a homotrimer. Here we report on second-site mutations in E1 that rescue the H230A mutant. These mutations were located in a cluster within the hinge region, at the membrane-interacting tip, and within the groove where the E1 stem is believed to pack. Together the revertants reveal specific and interconnected aspects of the fusion protein refolding reaction.
Chanel-Vos
Chantal
C
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Kielian
Margaret
M
D006639:Histidine / Q000235:genetics; D008561:Membrane Fusion / Q000235:genetics*; D050576:Membrane Fusion Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D011487:Protein Conformation; D017510:Protein Folding; D020673:Protein Renaturation; D012672:Semliki forest virus / Q000235:genetics* / Q000502:physiology; D014764:Viral Proteins
D050576:Membrane Fusion Proteins; D014764:Viral Proteins; D006639:Histidine