Mechanisms of influenza viral membrane fusion
Influenza viral particles are enveloped by a lipid bilayer. A major step in infection is fusion of the viral and host cellular membranes, a process with large kinetic barriers. Influenza membrane fusion is catalyzed by hemagglutinin (HA), a class I viral fusion protein activated by low pH. The exact nature of the HA conformational changes that deliver the energy required for fusion remains poorly understood. This review summarizes our current knowledge of HA structure and dynamics, describes recent single-particle experiments and modeling studies, and discusses their role in understanding how multiple HAs mediate fusion. These approaches provide a mechanistic picture in which HAs independently and stochastically insert into the target membrane, forming a cluster of HAs that is collectively able to overcome the barrier to membrane fusion. The new experimental and modeling approaches described in this review hold promise for a more complete understanding of other viral fusion systems and the protein systems responsible for cellular fusion.
1.Virus is taken up into a compartment in a cell, and proteins on the outside of the virus then gain access to the cell by fusing the virus- and cell- membranes.
2. Round virus particle covered with the proteins (left) and a schematic on the right similar to what we sent you before.
3. Both schematically and in a "smooth" fashion, one of the intermediates of interest: hemifusion of the membranes
4. Pore formation (or complete fusion)
