Leporipoxvirus Cu-Zn superoxide dismutase homologs inhibit cellular superoxide dismutase, but are not essential for virus replication or virulence.
Vertebrate poxviruses encode homologs of cellular cupro-zinc superoxide dismutases (Cu-Zn SOD). In this study we have examined the molecular genetic properties of two Cu-Zn SOD homologs encoded by the Shope fibroma virus (SFV) and myxoma virus. These Leporipoxvirus proteins should be catalytically inactive as judged by the point mutations which alter a key catalytic arginine and restructure the predicted Cu-binding domain. This prediction was confirmed using in situ gel assays and recombinant proteins produced both in bacteria and in mammalian cells. Western blot analysis showed that these proteins are produced in abundance late in infection and can, upon exposure to oxidizing conditions, form disulfide cross-linked dimers. They are also virion components and not essential for growth in culture or virulence. Leporipoxvirus Cu-Zn SOD homologs affected two phenotypes. First, deletion of the myxoma M131R gene caused the mutant virus to grow better ( approximately 10-fold) in culture than does the wild-type parent. Second, expression of either native or recombinant Leporipoxvirus proteins is accompanied by a decline in cellular Cu-Zn SOD activity. We concluded that these gene products can somehow modulate the activity of host Cu-Zn SODs, but what advantage is thus gained by the virus remains to be established.
Cao
Jing Xin
JX
Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada.
Teoh
Melissa L T
ML
Moon
Mijin
M
McFadden
Grant
G
Evans
David H
DH
D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015536:Down-Regulation; D012776:Fibroma Virus, Rabbit / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D016679:Genome, Viral; D000882:Haplorhini; D018152:Leporipoxvirus / Q000201:enzymology / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D009233:Myxoma virus / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D014779:Virus Replication
D013482:Superoxide Dismutase