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PDBsum entry 2m0s
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Viral protein
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PDB id
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2m0s
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References listed in PDB file
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Key reference
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Title
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Membrane topology and function of dengue virus ns2a protein.
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Authors
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X.Xie,
S.Gayen,
C.Kang,
Z.Yuan,
P.Y.Shi.
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Ref.
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J Virol, 2013,
87,
4609-4622.
[DOI no: ]
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PubMed id
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Abstract
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Flavivirus nonstructural protein 2A (NS2A) is a component of the viral
replication complex that functions in virion assembly and antagonizes the host
immune response. Although flavivirus NS2A is known to associate with the
endoplasmic reticulum (ER) membrane, the detailed topology of this protein has
not been determined. Here we report the first topology model of flavivirus NS2A
on the ER membrane. Using dengue virus (DENV) NS2A as a model, we show that (i)
the N-terminal 68 amino acids are located in the ER lumen, with one segment
(amino acids 30 to 52) that interacts with ER membrane without traversing the
lipid bilayer; (ii) amino acids 69 to 209 form five transmembrane segments, each
of which integrally spans the ER membrane; and (iii) the C-terminal tail (amino
acids 210 to 218) is located in the cytosol. Nuclear magnetic resonance (NMR)
structural analysis showed that the first membrane-spanning segment (amino acids
69 to 93) consists of two helices separated by a "helix breaker." The
helix breaker is formed by amino acid P85 and one positively charged residue,
R84. Functional analysis using replicon and genome-length RNAs of DENV-2
indicates that P85 is not important for viral replication. However, when R84 was
replaced with E, the mutation attenuated both viral RNA synthesis and virus
production. Remarkably, an R84A mutation did not affect viral RNA synthesis but
blocked intracellular formation of infectious virions. Collectively, the
mutagenesis results demonstrate that NS2A functions in both DENV RNA synthesis
and virion assembly/maturation. The topology model of DENV NS2A provides a good
starting point for studying how flavivirus NS2A modulates viral replication and
evasion of host immune response.
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