title: The stoichiometry of Gag protein in HIV-1.
abstract: The major structural components of HIV-1 are encoded as a single polyprotein, Gag, which is sufficient for virus particle assembly. Initially, Gag forms an approximately spherical shell underlying the membrane of the immature particle. After proteolytic maturation of Gag, the capsid (CA) domain of Gag reforms into a conical shell enclosing the RNA genome. This mature shell contains 1,000-1,500 CA proteins assembled into a hexameric lattice with a spacing of 10 nm. By contrast, little is known about the structure of the immature virus. We used cryo-EM and scanning transmission EM to determine that an average (145 nm diameter) complete immature HIV particle contains approximately 5,000 structural (Gag) proteins, more than twice the number from previous estimates. In the immature virus, Gag forms a hexameric lattice with a spacing of 8.0 nm. Thus, less than half of the CA proteins form the mature core.
authors.affiliation: Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford OX3 7BN, UK.
authors.forename: John A G
authors.initials: JA
authors.lastname: Briggs
authors.forename: Martha N
authors.initials: MN
authors.lastname: Simon
authors.forename: Ingolf
authors.initials: I
authors.lastname: Gross
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Kräusslich
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Fuller
authors.forename: Volker M
authors.initials: VM
authors.lastname: Vogt
authors.forename: Marc C
authors.initials: MC
authors.lastname: Johnson
mesh_terms: D020285:Cryoelectron Microscopy; D015683:Gene Products, gag / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning
chemical_list: D015683:Gene Products, gag