title: Characterization of a unique group-specific protein (U122) of the severe acute respiratory syndrome coronavirus.
abstract: A novel coronavirus (CoV) has been identified as the etiological agent of severe acute respiratory syndrome (SARS). The SARS-CoV genome encodes the characteristic essential CoV replication and structural proteins. Additionally, the genome contains six group-specific open reading frames (ORFs) larger than 50 amino acids, with no known homologues. As with the group-specific genes of the other CoVs, little is known about the SARS-CoV group-specific genes. SARS-CoV ORF7a encodes a putative unique 122-amino-acid protein, designated U122 in this study. The deduced sequence contains a probable cleaved signal sequence and a C-terminal transmembrane helix, indicating that U122 is likely to be a type I membrane protein. The C-terminal tail also contains a typical endoplasmic reticulum (ER) retrieval motif, KRKTE. U122 was expressed in SARS-CoV-infected Vero E6 cells, as it could be detected by Western blot and immunofluorescence analyses. U122 is localized to the perinuclear region of both SARS-CoV-infected and transfected cells and colocalized with ER and intermediate compartment markers. Mutational analyses showed that both the signal peptide sequence and ER retrieval motif were functional.
authors.affiliation: Collaborative Anti-Viral Research Group, Institute of Molecular and Cell Biology, Singapore 117609, Republic of Singapore.
authors.forename: Burtram C
authors.initials: BC
authors.lastname: Fielding
authors.forename: Yee-Joo
authors.initials: YJ
authors.lastname: Tan
authors.forename: Shen
authors.initials: S
authors.lastname: Shuo
authors.forename: Timothy H P
authors.initials: TH
authors.lastname: Tan
authors.forename: Eng-Eong
authors.initials: EE
authors.lastname: Ooi
authors.forename: Seng Gee
authors.initials: SG
authors.lastname: Lim
authors.forename: Wanjin
authors.initials: W
authors.lastname: Hong
authors.forename: Phuay-Yee
authors.initials: PY
authors.lastname: Goh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D021382:Protein Sorting Signals; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D013045:Species Specificity; D014162:Transfection; D014709:Vero Cells; D014763:Viral Matrix Proteins; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D021382:Protein Sorting Signals; D014763:Viral Matrix Proteins; D014764:Viral Proteins; C488151:sars7a protein, SARS virus