The prefusion structure of herpes simplex virus glycoprotein B

Abstract

Cell entry of enveloped viruses requires specialized viral proteins that mediate fusion with the host membrane by substantial structural rearrangements from a metastable pre- to a stable postfusion conformation. This metastability renders the herpes simplex virus 1 (HSV-1) fusion glycoprotein B (gB) highly unstable such that it readily converts into the postfusion form, thereby precluding structural elucidation of the pharmacologically relevant prefusion conformation. By identification of conserved sequence signatures and molecular dynamics simulations, we devised a mutation that stabilized this form. Functionally locking gB allowed the structural determination of its membrane-embedded prefusion conformation at sub-nanometer resolution and enabled the unambiguous fit of all ectodomains. The resulting pseudo-atomic model reveals a notable conservation of conformational domain rearrangements during fusion between HSV-1 gB and the vesicular stomatitis virus glycoprotein G, despite their very distant phylogeny. In combination with our comparative sequence-structure analysis, these findings suggest common fusogenic domain rearrangements in all class III viral fusion proteins.

Influence of N-glycosylation on Expression and Function of Pseudorabies Virus Glycoprotein gB

“…Herpesvirus gB is believed to undergo extensive conformational changes for fusion and is reported to transit from a (predicted) trimeric pre- to a trimeric post-fusion form [ 5 ]. Only recently, the pre-fusion structure of HSV-1 gB was reported [ 24 ]. Here, the HSV-1 pre-fusion gB structure was used as a template to generate a model for pre-fusion PrV gB ( Figure 1 C).…”

“…The yellow star indicates the furin-cleavage site. ( C ) Model of pre-fusion PrV gB trimer (left panel) was generated using the protein structure homology-modeling server SWISS-MODEL [ 26 ] and the pre-fusion structure of HSV-1 gB as template [ 24 ]. Domains I–V of one protomer (right panel) are colored as in ( A , B ), and the predicted glycosylation sites are shown as purple spheres, and the furin-cleavage site is marked by a yellow star.…”

“…Based on these structural studies, gB was identified as a class III fusion protein [ 22 ]. In contrast to the well-characterized post-fusion conformation, structural information on the gB pre-fusion conformation is limited to HSV-1 [ 23 , 24 ] and the betaherpesvirus human cytomegalovirus (HCMV) gB [ 25 ].…”

Prefusion structure of human cytomegalovirus glycoprotein B and structural basis for membrane fusion

“…A high-resolution structure of prefusion VSV G reveals a tripod-like architecture, with exposed fusion loops pointing toward the anchoring membrane ( 13 ). High-resolution herpesvirus gB prefusion structures have been elusive, although ~9- to 20-Å-resolution electron cryotomography (cryo-ET) molecular envelopes of surface glycoproteins on HSV-1 and CMV virions and of a mutation-stabilized prefusion HSV-1 gB on extracellular vesicles indicate that prefusion herpesvirus gBs also have tripod-like structures and an arrangement of domains like that of VSV G ( 6 , 14 , 15 ).…”

DNA origami signposts for identifying proteins on cell membranes by electron cryotomography

“…Vesicles displaying membrane-embedded target proteins were produced by using the MPEEV (membrane protein-enriched extracellular vesicles) system ( Zeev-Ben-Mordehai et al., 2014a ), exploiting endogenous extracellular vesicle production during membrane protein overexpression. We have used these vesicles previously for structural characterization of HSV-1 gB ( Vollmer et al., 2020 ; Zeev-Ben-Mordehai et al., 2016 ) and C. elegans cell-cell fusion protein EFF-1 ( Zeev-Ben-Mordehai et al., 2014b ). We created tagged versions of gB with sfGFP or mCherry inserted after the 30-residue N-terminal signal sequence.…”