PMID:21593161

Citation	Albright, BS, Nellissery, J, Szczepaniak, R and Weller, SK (2011) Disulfide bond formation in the herpes simplex virus 1 UL6 protein is required for portal ring formation and genome encapsidation. J. Virol. 85:8616-24
Abstract	The herpes simplex virus 1 (HSV-1) UL6 portal protein forms a 12-subunit ring structure at a unique capsid vertex which functions as a conduit for the encapsidation of the viral genome. We have demonstrated previously that the leucine zipper region of UL6 is important for intersubunit interactions and stable ring formation (J. K. Nellissery, R. Szczepaniak, C. Lamberti, and S. K. Weller, J. Virol. 81:8868-8877, 2007). We now demonstrate that intersubunit disulfide bonds exist between monomeric subunits and contribute to portal ring formation and/or stability. Intersubunit disulfide bonds were detected in purified portal rings by SDS-PAGE under nonreducing conditions. Furthermore, the treatment of purified portal rings with dithiothreitol (DTT) resulted in the disruption of the rings, suggesting that disulfide bonds confer stability to this complex structure. The UL6 protein contains nine cysteines that were individually mutated to alanine. Two of these mutants, C166A and C254A, failed to complement a UL6 null mutant in a transient complementation assay. Furthermore, viral mutants bearing the C166A and C254A mutations failed to produce infectious progeny and were unable to cleave or package viral DNA. In cells infected with C166A or C254A, B capsids were produced which contained UL6 at reduced levels compared to those seen in wild-type capsids. In addition, C166A and C254A mutant proteins expressed in insect cells infected with recombinant baculovirus failed to form ring structures. Cysteines at positions 166 and 254 thus appear to be required for intersubunit disulfide bond formation. Taken together, these results indicate that disulfide bond formation is required for portal ring formation and/or stability and for the production of procapsids that are capable of encapsidation.
Links	PubMed PMC3165836 Online version:10.1128/JVI.00123-11
Keywords	Amino Acid Substitution/genetics; Animals; Cell Line; Cysteine/genetics; Disulfides/metabolism; Electrophoresis, Polyacrylamide Gel; Gene Deletion; Genetic Complementation Test; Herpesvirus 1, Human/physiology; Mutagenesis, Site-Directed; Protein Multimerization; Protein Stability; Protein Subunits/metabolism; Viral Proteins/chemistry; Viral Proteins/metabolism; Virus Assembly
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HHV11:PORTL		GO:0042025: host cell nucleus	ECO:0000314:		C		Figure 5B shows that as previously reported, wild-type UL6 localizes to the nucleus of transfected cells even in the absence of other viral proteins.	complete CACAO 9445

References

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