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An unconventional role for cytoplasmic disulfide bonds in vaccinia virus proteins.

Locker JK, Griffiths G - J. Cell Biol. (1999)

Bottom Line: Previous data have shown that reducing agents disrupt the structure of vaccinia virus (vv).Under these conditions, however, the membranes around the isolated particles appeared less stable and detached from the underlying core.Our data show that vv has evolved an unique system for the assembly of cytoplasmic disulfide bonds that are localized both on the exterior and interior parts of the IMV.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Cell Biology Programme, 69117 Heidelberg, Germany. krijnse@embl-heidelberg.de

ABSTRACT
Previous data have shown that reducing agents disrupt the structure of vaccinia virus (vv). Here, we have analyzed the disulfide bonding of vv proteins in detail. In vv-infected cells cytoplasmically synthesized vv core proteins became disulfide bonded in the newly assembled intracellular mature viruses (IMVs). vv membrane proteins also assembled disulfide bonds, but independent of IMV formation and to a large extent on their cytoplasmic domains. If disulfide bonding was prevented, virus assembly was only partially impaired as shown by electron microscopy as well as a biochemical assay of IMV formation. Under these conditions, however, the membranes around the isolated particles appeared less stable and detached from the underlying core. During the viral infection process the membrane proteins remained disulfide bonded, whereas the core proteins were reduced, concomitant with delivery of the cores into the cytoplasm. Our data show that vv has evolved an unique system for the assembly of cytoplasmic disulfide bonds that are localized both on the exterior and interior parts of the IMV.

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Schematic representation of the IMV structure. The  brick-shaped core in the central part is made up predominantly  by the proteins 4a, 4b, p25, and p11. The core is studded with a  layer of spikes that consists at least in part of the p39 protein. The  particle is surrounded by two cisternal membrane layers that we  believe do not fused with themselves (which is depicted in this  figure as a hypothetical overlapping of the cisternal membranes).  The inner of the two membranes contains mainly p21 and p16,  the outer p35, p32, p8, and the peripheral membrane protein p14  (see also 50). In this model the cisternal envelope is akin to the  two membranes of the nuclear envelope, continuous but distinct  in protein composition.
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Figure 1: Schematic representation of the IMV structure. The brick-shaped core in the central part is made up predominantly by the proteins 4a, 4b, p25, and p11. The core is studded with a layer of spikes that consists at least in part of the p39 protein. The particle is surrounded by two cisternal membrane layers that we believe do not fused with themselves (which is depicted in this figure as a hypothetical overlapping of the cisternal membranes). The inner of the two membranes contains mainly p21 and p16, the outer p35, p32, p8, and the peripheral membrane protein p14 (see also 50). In this model the cisternal envelope is akin to the two membranes of the nuclear envelope, continuous but distinct in protein composition.

Mentions: Vaccinia virus (vv), the best studied member of the poxviridae, is the largest and most complex of animal viruses known, measuring ∼350 nm in its largest dimension. It contains a dsDNA genome of ∼190 kB encoding for >200 proteins, of which ∼100 seem to be associated with the virion (14). vv is unique in that during its life cycle two infectious forms are made, the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV; 40). We have recently shown that the IMV membranes are derived from the intermediate compartment (IC) located between the ER and the Golgi complex (53), a finding that is consistent with the fact that at least three of its membrane proteins insert cotranslationally into the RER and are retained in the IC in infected cells (34, 51). Although the detailed structure of the IMV is unknown, it is generally accepted that the virion is composed of a membrane-enclosed, brick-shaped core that contains four particularly abundant proteins, 4a (gene A10L), 4b (A3L), and the 11-kD (F17R) and 25-kD (L4R) putative DNA-binding proteins (see Fig. 1 and Table I). The surface of the viral core is studded with a spike-like structure, that comprises, at least in part, an abundant 39-kD protein (A4L; 8, 50). The IC-derived cisternal membranes that surround the core contain three highly abundant membrane proteins of 16 (A14L), 21 (A17L), and 8 (A13L) kD (26, 51), as well as a peripheral membrane protein p14 (A27L; 47, 49, 54). Furthermore the IMV membrane contains a set of less abundant membrane proteins such as p32 (D8L; 43), p35 (H3L; 4), and a 27-kD myristoylated protein (L1R; 60; see Fig. 1 and Table I).


An unconventional role for cytoplasmic disulfide bonds in vaccinia virus proteins.

Locker JK, Griffiths G - J. Cell Biol. (1999)

Schematic representation of the IMV structure. The  brick-shaped core in the central part is made up predominantly  by the proteins 4a, 4b, p25, and p11. The core is studded with a  layer of spikes that consists at least in part of the p39 protein. The  particle is surrounded by two cisternal membrane layers that we  believe do not fused with themselves (which is depicted in this  figure as a hypothetical overlapping of the cisternal membranes).  The inner of the two membranes contains mainly p21 and p16,  the outer p35, p32, p8, and the peripheral membrane protein p14  (see also 50). In this model the cisternal envelope is akin to the  two membranes of the nuclear envelope, continuous but distinct  in protein composition.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132897&req=5

Figure 1: Schematic representation of the IMV structure. The brick-shaped core in the central part is made up predominantly by the proteins 4a, 4b, p25, and p11. The core is studded with a layer of spikes that consists at least in part of the p39 protein. The particle is surrounded by two cisternal membrane layers that we believe do not fused with themselves (which is depicted in this figure as a hypothetical overlapping of the cisternal membranes). The inner of the two membranes contains mainly p21 and p16, the outer p35, p32, p8, and the peripheral membrane protein p14 (see also 50). In this model the cisternal envelope is akin to the two membranes of the nuclear envelope, continuous but distinct in protein composition.
Mentions: Vaccinia virus (vv), the best studied member of the poxviridae, is the largest and most complex of animal viruses known, measuring ∼350 nm in its largest dimension. It contains a dsDNA genome of ∼190 kB encoding for >200 proteins, of which ∼100 seem to be associated with the virion (14). vv is unique in that during its life cycle two infectious forms are made, the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV; 40). We have recently shown that the IMV membranes are derived from the intermediate compartment (IC) located between the ER and the Golgi complex (53), a finding that is consistent with the fact that at least three of its membrane proteins insert cotranslationally into the RER and are retained in the IC in infected cells (34, 51). Although the detailed structure of the IMV is unknown, it is generally accepted that the virion is composed of a membrane-enclosed, brick-shaped core that contains four particularly abundant proteins, 4a (gene A10L), 4b (A3L), and the 11-kD (F17R) and 25-kD (L4R) putative DNA-binding proteins (see Fig. 1 and Table I). The surface of the viral core is studded with a spike-like structure, that comprises, at least in part, an abundant 39-kD protein (A4L; 8, 50). The IC-derived cisternal membranes that surround the core contain three highly abundant membrane proteins of 16 (A14L), 21 (A17L), and 8 (A13L) kD (26, 51), as well as a peripheral membrane protein p14 (A27L; 47, 49, 54). Furthermore the IMV membrane contains a set of less abundant membrane proteins such as p32 (D8L; 43), p35 (H3L; 4), and a 27-kD myristoylated protein (L1R; 60; see Fig. 1 and Table I).

Bottom Line: Previous data have shown that reducing agents disrupt the structure of vaccinia virus (vv).Under these conditions, however, the membranes around the isolated particles appeared less stable and detached from the underlying core.Our data show that vv has evolved an unique system for the assembly of cytoplasmic disulfide bonds that are localized both on the exterior and interior parts of the IMV.

View Article: PubMed Central - PubMed

Affiliation: European Molecular Biology Laboratory, Cell Biology Programme, 69117 Heidelberg, Germany. krijnse@embl-heidelberg.de

ABSTRACT
Previous data have shown that reducing agents disrupt the structure of vaccinia virus (vv). Here, we have analyzed the disulfide bonding of vv proteins in detail. In vv-infected cells cytoplasmically synthesized vv core proteins became disulfide bonded in the newly assembled intracellular mature viruses (IMVs). vv membrane proteins also assembled disulfide bonds, but independent of IMV formation and to a large extent on their cytoplasmic domains. If disulfide bonding was prevented, virus assembly was only partially impaired as shown by electron microscopy as well as a biochemical assay of IMV formation. Under these conditions, however, the membranes around the isolated particles appeared less stable and detached from the underlying core. During the viral infection process the membrane proteins remained disulfide bonded, whereas the core proteins were reduced, concomitant with delivery of the cores into the cytoplasm. Our data show that vv has evolved an unique system for the assembly of cytoplasmic disulfide bonds that are localized both on the exterior and interior parts of the IMV.

Show MeSH
Related in: MedlinePlus