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1.G.5 The Viral Pore-forming Membrane Fusion Protein-5 (VMFP5) Family

The Vesicular Stomatitis Virus (VSV) G protein and the HSV-1gB fusion protein are of Class III. They do not require proteolytic processing for function and consist of both α- and β-structure. The native trimers remain trimers upon membrane insertion to promote pore formation and fusion (White et al. 2008).  The fusogenic transition entails an extensive structural reorganization of G (Roche et al., 2007).  In the prefusion form, G has the shape of a tripod with the fusion loops exposed, which point toward the viral membrane with the antigenic sites located at the distal end of the molecule. A large number of G glycoproteins, perhaps organized as in the crystals, act cooperatively to induce membrane merging. Fusion occurs in the endosome in response to the acidic pH.  The transmembrane domain in the G protein may induce positive intrinsic curvature and thereby induce formation of fusion pores (Sengupta et al. 2014).

References associated with 1.G.5 family:

Roche, S., F.A. Rey, Y. Gaudin, and S. Bressanelli. (2007). Structure of the prefusion form of the vesicular stomatitis virus glycoprotein G. Science 315: 843-848. 17289996
Sengupta, T., H. Chakraborty, and B.R. Lentz. (2014). The Transmembrane Domain Peptide of Vesicular Stomatitis Virus Promotes Both Intermediate and Pore Formation during PEG-Mediated Vesicle Fusion. Biophys. J. 107: 1318-1326. 25229140
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. 18568847