Identification of a novel protein 3a from severe acute respiratory syndrome coronavirus

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• The SARS-CoV genome contains an open reading frame 3 (ORF3) encoding a predicted protein 3a.
• Protein 3a has no significant similarity to known proteins, suggesting a unique function.

Purpose of the Study:

• To investigate the expression and localization of SARS-CoV protein 3a.
• To confirm protein 3a as a novel SARS-CoV-specific protein.

Main Methods:

• Generated specific antibodies against SARS protein 3a using a synthetic peptide (P2).
• Detected recombinant and endogenous protein 3a in Escherichia coli, Vero E6 cells, and patient lung specimens using Western blot and immunofluorescence.

Main Results:

• Specific antibodies successfully detected SARS protein 3a.
• Protein 3a expression was observed in infected Vero E6 cells starting at 8-12 hours post-infection, peaking around 24 hours.
• Protein 3a was localized in the cytoplasm and Golgi apparatus of infected cells and detected in lung tissues of SARS patients.

Conclusions:

• SARS-CoV expresses a novel protein 3a.
• Protein 3a is unique to SARS-CoV and not found in other coronaviruses.