1.G.2 The Viral Pore-forming Membrance Fusion Protein-2 (VMFP2) Family

Like the Influenza HA protein, the Paramyxovirus F protein is of Class I (White et al. 2008) and shares the characteristics noted in the description for family 1.H.1. It is the second best charaterized Class I viral fusion protein. The crystal structures of various ectodomains are known. The F protein consists of three domains, domains, I, II, and III (Lamb and Jardetzky, 2007).



Apellaniz B., Huarte N., Largo E. and Nieva JL. (2014). The three lives of viral fusion peptides. Chem Phys Lipids. 181:40-55.

Cifuentes-Muñoz, N., W. Sun, G. Ray, P.T. Schmitt, S. Webb, K. Gibson, R.E. Dutch, and A.P. Schmitt. (2017). Mutations in the Transmembrane Domain and Cytoplasmic Tail of Hendra Virus Fusion Protein Disrupt Virus-Like-Particle Assembly. J. Virol. 91:.

Coropceanu, I., E.M. Janke, J. Portner, D. Haubold, T.D. Nguyen, A. Das, C.P.N. Tanner, J.K. Utterback, S.W. Teitelbaum, M.H. Hudson, N.A. Sarma, A.M. Hinkle, C.J. Tassone, A. Eychmüller, D.T. Limmer, M. Olvera de la Cruz, N.S. Ginsberg, and D.V. Talapin. (2022). Self-assembly of nanocrystals into strongly electronically coupled all-inorganic supercrystals. Science 375: 1422-1426.

Crampon, E., E. Covernton, M.C. Vaney, M. Dellarole, S. Sommer, A. Sharma, A. Haouz, P. England, J. Lepault, S. Duquerroy, F.A. Rey, and G. Barba-Spaeth. (2023). New insight into flavivirus maturation from structure/function studies of the yellow fever virus envelope protein complex. mBio e0070623. [Epub: Ahead of Print]

Lamb, R.A. and T.S. Jardetzky. (2007). Structural basis of viral invasion: lessons from paramyxovirus F. Curr. Opin. Struct. Biol. 17: 427-436.

Li Z., Hung C., Paterson RG., Michel F., Fuentes S., Place R., Lin Y., Hogan RJ., Lamb RA. and He B. (2015). Type II integral membrane protein, TM of J paramyxovirus promotes cell-to-cell fusion. Proc Natl Acad Sci U S A. 112(40):12504-9.

McLellan, J.S., M. Chen, S. Leung, K.W. Graepel, X. Du, Y. Yang, T. Zhou, U. Baxa, E. Yasuda, T. Beaumont, A. Kumar, K. Modjarrad, Z. Zheng, M. Zhao, N. Xia, P.D. Kwong, and B.S. Graham. (2013). Structure of RSV fusion glycoprotein trimer bound to a prefusion-specific neutralizing antibody. Science 340: 1113-1117.

Saier, M.H., Jr, V.S. Reddy, B.V. Tsu, M.S. Ahmed, C. Li, and G. Moreno-Hagelsieb. (2016). The Transporter Classification Database (TCDB): recent advances. Nucleic Acids Res 44: D372-379.

von Messling, V., D. Milosevic, P. Devaux, and R. Cattaneo. (2004). Canine distemper virus and measles virus fusion glycoprotein trimers: partial membrane-proximal ectodomain cleavage enhances function. J. Virol. 78: 7894-7903.

White, J.M., S.E. Delos, M. Brecher, and K. Schornberg. (2008). Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit. Rev. Biochem. Mol. Biol. 43: 189-219.

Yao, H., M. Lee, S.Y. Liao, and M. Hong. (2016). Solid-State NMR Investigation of the Structural Topology and Lipid Interactions of a Viral Fusion Protein Chimera Containing the Fusion Peptide and Transmembrane Domain. Biochemistry. [Epub: Ahead of Print]


TC#NameOrganismal TypeExample
1.G.2.1.1The Paramyxovirus (Class I) fusion (F) protein (545 aas)VirusProtein F of Paramyxovirus (Q5S8E4)

Fusion glycoprotein FO (Class I) (565 aas) (31% identical throughout its length with 1.H.2.1.1) (Lamb and Jardetzky 2007).  Interacts with protein G and protein TM in J paramyxovirus to promote fusion (Li et al. 2015).



The respiratory syncytial virus (RSV) fusion (F) glycoprotein.  The crystal strcuture is available (McLellan et al. 2013).  The protein has at least 3 conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and plasma cell membrane fusion, the heptad repeat (HR) regions assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and plasma cell membranes which leads to delivery of the nucleocapsid into the cytoplasm. Fusion is pH independent and occurs directly at the outer cell membrane. The trimer of F1-F2 (protein F) interacts with glycoprotein G at the virion surface. Upon binding of G to heparan sulfate, the hydrophobic fusion peptide is unmasked and interacts with the cellular membrane, inducing the fusion between host cell and virion membranes. RSV fusion protein is able to interact directly with heparan sulfate and therefore actively participates in virus attachment.


F-glycoprotein of respiatory syncytial virus


The fusion glycoprotein F0 of 94 aas


F0 of Newcastle Disease Virus


Fusion glycoprotein F0 of 550 aas


Fusion glycoprotein of Measles virus


Fusion glycoprotein of 529 aas (Apellániz et al. 2014). Loosely associated fusion peptide and TMS helices generate significant negative Gaussian curvature to membranes that possess spontaneous positive curvature, consistent with fusion peptide-TMS assembly facilitating the transition of the membrane from hemifusion intermediates to the fusion pore (Yao et al. 2016).

Viruses (Orthomyxoviridae)

Fusion protein of influenza virus 5 (PIV5)


Fusion glycoprotein F0 of 546 aas and 2 TMSs (N- and C-terminal) (Apellániz et al. 2014). The unique endocytic trafficking pathway of Hendra virus F protein is required for proper viral assembly and particle release (Cifuentes-Muñoz et al. 2017).

Viruses (Paramyxoviridae)

F0 of Hendra virus


Fusion glycoprotein, F, of 111 aas and 1 C-terminal TMS as well as two small peaks of moderate hydrophobicity in the N-terminal and central regions of the protein. The trimeric fusion, F, glycoproteins of morbilliviruses are activated by furin cleavage of the precursor F0 into the F1 and F2 subunits, and an additional membrane-proximal cleavage occurs and modulates F protein function (von Messling et al. 2004).

Fusion GP of Canine morbillivirus


The fusion (F) protein (602 aas and 3 very hydrophobic TMSs, one N-terminal, one at residue 120 and one C-terminal, plus 5 moderately hydrophobic peaks at residies 240 - 470, of the zoonotic Nipah virus, that together with the G (glyco)-protein (546 aas and 1 N-terminal TMS; Q9IH62) are essential for viral entry into human and animal cells (Coropceanu et al. 2022).

F-protein of Nepah virus


TC#NameOrganismal TypeExample

Baseplate J/gp47 family protein of 374 aa

Gp47 family protein of Providencia stuartii