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. Author manuscript; available in PMC: 2017 Sep 1.
Published in final edited form as: Curr Clin Microbiol Rep. 2016 Jul 5;3(3):142–154. doi: 10.1007/s40588-016-0040-8

Fig. 6. Model of the late steps in paramyxovirus membrane fusion.

Fig. 6

Inner and outer membrane leaflets of viral and cellular membranes are shown as green and brown, respectively. The attachment protein is shown with a green stalk and purple head, while yellow depicts its bound receptor. For F, the cytoplasmic tail (CT), transmembrane (TM) domain, and HR2 are shown in blue. The head region through HR1 is shown in red and the fusion peptide in orange. A) The attachment glycoprotein binds its receptor and triggers prefusion F. B) To reach the prehairpin intermediate (PHI), HR2 melts and forms an open stalk. HR1 extends and projects the fusion peptide into the target membrane. (C) The head continues to refold, bringing HR1 and HR2 into close proximity, and pulls the membranes in. (D) HR1 and HR2 “zipper” together and the outer membranes fuse to form the hemifusion intermediate. (E) Inner membranes fuse as zippering continues through the transmembrane domain, forming the 6-helix bundle. F’s CT is now exposed to intracellular proteins and the fusion pore expands. The actin cytoskeleton (shown in light green) is likely involved in fusion pore expansion.