Abstract
The open reading frame (ORF) 7a of the SARS-associated coronavirus (SARS-CoV) encodes a unique type I transmembrane protein of unknown function. We have determined the 1.8 A resolution crystal structure of the N-terminal ectodomain of orf7a, revealing a compact seven-stranded beta sandwich unexpectedly similar in fold and topology to members of the Ig superfamily. We also demonstrate that, in SARS-CoV- infected cells, the orf7a protein is expressed and retained intracellularly. Confocal microscopy studies using orf7a and orf7a/CD4 chimeras implicate the short cytoplasmic tail and transmembrane domain in trafficking of the protein within the endoplasmic reticulum and Golgi network. Taken together, our findings provide a structural and cellular framework in which to explore the role of orf7a in SARS-CoV pathogenesis.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Antibodies, Monoclonal / biosynthesis
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Cells, Cultured
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Chlorocebus aethiops
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Crystallography, X-Ray
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Cytoplasm / metabolism
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Endoplasmic Reticulum / metabolism
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Flow Cytometry
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Golgi Apparatus / metabolism
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Humans
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Mass Spectrometry
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Membrane Proteins / chemistry
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Membrane Proteins / genetics*
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Membrane Proteins / metabolism*
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Mice
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Mice, Inbred BALB C
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Microscopy, Confocal
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Models, Molecular
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Open Reading Frames*
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Precipitin Tests
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Protein Structure, Secondary
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Protein Structure, Tertiary
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Sequence Analysis, Protein
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Severe acute respiratory syndrome-related coronavirus / genetics
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Severe acute respiratory syndrome-related coronavirus / metabolism*
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Vero Cells
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Viral Proteins / genetics
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Viral Proteins / metabolism*
Substances
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Antibodies, Monoclonal
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Membrane Proteins
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ORF7b protein, SARS coronavirus
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Recombinant Fusion Proteins
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Viral Proteins