Artikel
Efficient transport of a novel SARS coronavirus protein, U274, to the cell surface
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Veröffentlicht: | 26. Mai 2004 |
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Gliederung
Text
The SARS-CoV genome contains open reading frames (ORFs) that encode for several genes that are homologous to proteins found in all known coronaviruses. These are the replicase gene 1a/1b and the 4 structural proteins, nucleocapsid (N), spike (S), membrane (M) and envelope (E), and these proteins are expected to be essential for the replication of the virus. In addition, it also contains 10 potential ORFs varying in length from 39 to 274 amino acids. The largest among these is the first ORF of the second longest subgenomic RNA and this protein (termed U274 in this study) consists of 274 amino acids and contains 3 putative transmembrane domains. Using antibody specific for the C-terminus of U274, U274 was shown to be expressed in SARS-CoV infected Vero E6 cells. Besides the full-length protein, two other processed forms were also detected. Using direct immunoflurorescence, U274 was localized to the perinuclear region as well as to the plasma membrane, in both transfected and infected cells. A N-terminus myc-tagged U274 was used to confirm the topology of U274 and to show that it is expressed on the surface in fixed and unpermeabilized cells. FACS scan analysis also showed that myc-U274 was expressed on the surface of live cells. In addition, U274 can interact specifically with the M and E proteins, as well as with U122, another protein unique to SARS-CoV. U274 can also undergo self-dimerization.