Structure and intracellular targeting of the SARS-coronavirus Orf7a accessory protein

Structure. 2005 Jan;13(1):75-85. doi: 10.1016/j.str.2004.10.010.


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

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / biosynthesis
  • Cells, Cultured
  • Chlorocebus aethiops
  • Crystallography, X-Ray
  • Cytoplasm / metabolism
  • Endoplasmic Reticulum / metabolism
  • Flow Cytometry
  • Golgi Apparatus / metabolism
  • Humans
  • Mass Spectrometry
  • Membrane Proteins / chemistry
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Confocal
  • Models, Molecular
  • Open Reading Frames*
  • Precipitin Tests
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Sequence Analysis, Protein
  • Severe acute respiratory syndrome-related coronavirus / genetics
  • Severe acute respiratory syndrome-related coronavirus / metabolism*
  • Vero Cells
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*


  • Antibodies, Monoclonal
  • Membrane Proteins
  • ORF7b protein, SARS coronavirus
  • Recombinant Fusion Proteins
  • Viral Proteins

Associated data

  • PDB/1XAK