Turning of the receptor-binding domains opens up the murine leukaemia virus Env for membrane fusion

Wu, Shang; Sjöberg, Mathilda; Wallin, Michael; Lindqvist, Birgitta; Ekström, Maria; Hebert, Hans; Koeck, Philip J.B.; Garoff, Henrik

doi:10.1038/emboj.2008.187

Cited by 15 publications

(38 citation statements)

References 51 publications

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“…It is compared with the structure of the mature Env with the R-peptide cleaved, which we have determined earlier (Fig. 1C, Right) (11). The R-peptide Env showed a similar open cage-like structure as the mature one.…”

Section: Resultsmentioning

confidence: 99%

“…However, the bottom protrusion did not form the separated Env legs typical for the mature virus, but rather converged into a common central body. The atomic structure of the RBD of Friend-MLV has been determined and used to model the structure of the Mo-MLV RBD (11). It is shaped like a bent finger and has earlier been fitted into the upper protrusion of the mature Env.…”

Section: Resultsmentioning

confidence: 99%

“…If an alkylator is present during Env triggering, the isomerization-active thiol becomes modified before it can attack the intersubunit disulfide and the Env will be arrested in its activation process at an intermediate stage, the isomerization-arrested stage (IAS). This form of the Env has also been studied by cryo-EM, and the structure shows that activation is initiated by a clockwise rotation of the RBDs, opening up the closed roof of the Env (11). Most likely, the rotation triggers the disulfide isomerization.…”

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confidence: 99%

“…The SU has been shown to consist of a receptor-binding N-terminal domain (RBD) and a C-terminal domain (12). The atomic structure of the RBD has been solved and fits into the top protrusion, suggesting that the middle one represents the Cterminal SU domain and that the lower, forming the separated Env legs, represents the TM subunit (11,13).…”

mentioning

confidence: 99%

“…The structure of the MLV Env has been studied by cryoelectron microscopy (cryo-EM) both in intact particles and as solubilized trimers (10,11). It reveals a remarkably open structure with separated legs.…”

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confidence: 99%

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Maturation cleavage of the murine leukemia virus Env precursor separates the transmembrane subunits to prime it for receptor triggering

Löving

Wu²,

Sjöberg

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The Env protein of murine leukemia virus matures by two cleavage events. First, cellular furin separates the receptor binding surface (SU) subunit from the fusion-active transmembrane (TM) subunit and then, in the newly assembled particle, the viral protease removes a 16-residue peptide, the R-peptide from the endodomain of the TM. Both cleavage events are required to prime the Env for receptor-triggered activation. Cryoelectron microscopy (cryo-EM) analyses have shown that the mature Env forms an open cage-like structure composed of three SU-TM complexes, where the TM subunits formed separated Env legs. Here we have studied the structure of the R-peptide precursor Env by cryo-EM. TM cleavage in Moloney murine leukemia virus was inhibited by amprenavir, and the Envs were solubilized in Triton X-100 and isolated by sedimentation in a sucrose gradient. We found that the legs of the R-peptide Env were held together by trimeric interactions at the very bottom of the Env. This suggested that the R-peptide ties the TM legs together and that this prevents the activation of the TM for fusion. The model was supported by further cryo-EM studies using an R-peptide Env mutant that was fusion-competent despite an uncleaved R-peptide. The Env legs of this mutant were found to be separated, like in the mature Env. This shows that it is the TM leg separation, normally caused by R-peptide cleavage, that primes the Env for receptor triggering.three-dimensional structure | retrovirus | spike protein T he spike protein Env on the surface of the retrovirus murine leukemia virus (MLV) matures by two proteolytic cleavage events mediated by cellular furin and the viral protease (1-3). Env is composed of an 80-kDa transmembrane precursor protein in the rough endoplasmic reticulum of the infected cell (4, 5). Here it trimerizes before it is routed to the cell surface for assembly with the internal Gag and GagPol precursors into virus particles in a budding process (6). The furin cleavage of Env occurs in the trans-Golgi, and it separates the surface (SU) subunit from the transmembrane (TM) (Pr15E) subunit. This cleavage also releases the viral fusion peptide at the N-terminal end of the TM. The viral protease cleavage occurs after virus assembly in the newly formed particle. It removes a 16-residuelong peptide, the R-peptide from the C terminus of the TM, forming p15E (7). Not until this second cleavage is completed is Env primed for receptor-mediated triggering into further conformations that can direct virus entry through fusion of the viral membrane with the cell membrane (8, 9). The viral protease also cleaves the Gag and GagPol precursors into their mature proteins and enzymes.The structure of the MLV Env has been studied by cryoelectron microscopy (cryo-EM) both in intact particles and as solubilized trimers (10, 11). It reveals a remarkably open structure with separated legs. The protomer of the solubilized Env is formed from three protrusions-upper, middle, and lower. Together, they encage a large central cavity, with the top pro...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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