Mimivirus
Mimivirus is a genus of viruses, in the family Mimiviridae.
Amoeba serve as natural hosts.[1][2] This genus contains a single identified species named Acanthamoeba polyphaga mimivirus (APMV), which serves as its type species. It also refers to a group of phylogenetically related large viruses.[3]
In colloquial speech, APMV is more commonly referred to as just "mimivirus". Mimivirus, short for "mimicking microbe", is so called to reflect its large size and apparent Gram-staining properties.[4]
Mimivirus has a large and complex genome compared with most other viruses. Until 2013, when a larger virus Pandoravirus was described, it had the largest capsid diameter of all known viruses.[
Tämän jättikokoisen dsDNA viruksen Kupari-Sinkki SOD entsyymin apo-muoto, joka täydentyy siten isäntäkehosta saadeusta kuparista ja sinkistä täysin toimivaksi Cu,Zn, SOD entsyymiksi.
J Virol. 2015 Jan;89(1):824-32. doi: 10.1128/JVI.02588-14. Epub 2014 Oct 29.
The megavirus chilensis Cu,Zn-superoxide dismutase: the first viral structure of a typical cellular copper chaperone-independent hyperstable dimeric enzyme.
Giant
viruses able to replicate in Acanthamoeba castellanii penetrate their
host through phagocytosis. After capsid opening, a fusion between the
internal membranes of the virion
and the phagocytic vacuole triggers the transfer in the cytoplasm of
the viral DNA together with the DNA repair enzymes and the transcription
machinery present in the particles. In addition, the proteome analysis
of purified mimivirus virions
revealed the presence of many enzymes meant to resist oxidative stress
and conserved in the Mimiviridae. Megavirus chilensis encodes a
predicted copper,
zinc superoxide dismutase (Cu,Zn-SOD), an enzyme known to detoxify
reactive oxygen species released in the course of host defense
reactions. While it was thought that the metal ions are required for the
formation of the active-site lid and dimer stabilization, megavirus
chilensis SOD forms a very stable metal-free dimer. We used electron
paramagnetic resonance (EPR) analysis and activity measurements to show
that the supplementation of the bacterial culture with copper
and zinc during the recombinant expression of Mg277 is sufficient to
restore a fully active holoenzyme. These results demonstrate that the
viral enzyme's activation is independent of a chaperone both for
disulfide bridge formation and for copper
incorporation and suggest that its assembly may not be as regulated as
that of its cellular counterparts. A SOD protein is encoded by a variety
of DNA viruses but is absent from mimivirus. As in poxviruses, the
enzyme might be dispensable when the virus infects Acanthamoeba cells
but may allow megavirus chilensis to infect a broad range of eukaryotic
hosts. IMPORTANCE:
Mimiviridae are giant viruses encoding more than 1,000 proteins. The virion particles are loaded with proteins used by the virus to resist the vacuole's oxidative stress. The megavirus chilensis virion contains a predicted copper, zinc superoxide dismutase (Cu,Zn-SOD). The corresponding gene is present in some megavirus chilensis relatives but is absent from mimivirus. This first crystallographic structure of a viral Cu,Zn-SOD highlights the features that it has in common with and its differences from cellular SODs. It corresponds to a very stable dimer of the apo form of the enzyme. We demonstrate that upon supplementation of the growth medium with Cu and Zn, the recombinant protein is fully active, suggesting that the virus's SOD activation is independent of a copper chaperone for SOD generally used by eukaryotic SODs.
Mimiviridae are giant viruses encoding more than 1,000 proteins. The virion particles are loaded with proteins used by the virus to resist the vacuole's oxidative stress. The megavirus chilensis virion contains a predicted copper, zinc superoxide dismutase (Cu,Zn-SOD). The corresponding gene is present in some megavirus chilensis relatives but is absent from mimivirus. This first crystallographic structure of a viral Cu,Zn-SOD highlights the features that it has in common with and its differences from cellular SODs. It corresponds to a very stable dimer of the apo form of the enzyme. We demonstrate that upon supplementation of the growth medium with Cu and Zn, the recombinant protein is fully active, suggesting that the virus's SOD activation is independent of a copper chaperone for SOD generally used by eukaryotic SODs.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
- PMID:
- 25355875
- PMCID:
- PMC4301173
- DOI:
- 10.1128/JVI.02588-14
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