In vitro assembly of virus-like particles of a gammaretrovirus, the murine leukemia virus XMRV |
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Authors: | Hadravová Romana de Marco Alex Ulbrich Pavel Stokrová Jitka Dolezal Michal Pichová Iva Ruml Tomás Briggs John A G Rumlová Michaela |
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Institution: | Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., IOCB and Gilead Research Center, Prague, Czech Republic. |
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Abstract: | Immature retroviral particles are assembled by self-association of the structural polyprotein precursor Gag. During maturation the Gag polyprotein is proteolytically cleaved, yielding mature structural proteins, matrix (MA), capsid (CA), and nucleocapsid (NC), that reassemble into a mature viral particle. Proteolytic cleavage causes the N terminus of CA to fold back to form a β-hairpin, anchored by an internal salt bridge between the N-terminal proline and the inner aspartate. Using an in vitro assembly system of capsid-nucleocapsid protein (CANC), we studied the formation of virus-like particles (VLP) of a gammaretrovirus, the xenotropic murine leukemia virus (MLV)-related virus (XMRV). We show here that, unlike other retroviruses, XMRV CA and CANC do not assemble tubular particles characteristic of mature assembly. The prevention of β-hairpin formation by the deletion of either the N-terminal proline or 10 initial amino acids enabled the assembly of ΔProCANC or Δ10CANC into immature-like spherical particles. Detailed three-dimensional (3D) structural analysis of these particles revealed that below a disordered N-terminal CA layer, the C terminus of CA assembles a typical immature lattice, which is linked by rod-like densities with the RNP. |
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