Characterization of severe acute respiratory syndrome coronavirus membrane protein

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• The coronavirus membrane protein (M) is crucial for virion assembly at intracellular membranes.
• Understanding M protein glycosylation is essential for comprehending coronavirus replication and pathogenesis.

Purpose of the Study:

• To investigate the glycosylation status and intracellular trafficking of the SARS-CoV M protein.
• To characterize the N-glycosylation site and processing of M protein in infected cells and virions.

Main Methods:

• Utilized a newly developed human monoclonal anti-M antibody for detection.
• Analyzed M protein in SARS-CoV infected cells and purified virions.
• Investigated N-glycosylation using endoglycosidase H sensitivity assays.
• Studied recombinant M protein transport and glycosylation in host cells.

Main Results:

• Detected both glycosylated and nonglycosylated M protein in infected cells and virions.
• Identified a single N-glycosylation site at asparagine 4 (N4) on the M protein.
• Recombinant M protein was transported to the plasma membrane and acquired complex-type N-glycosylation.
• In infected cells and virions, M protein N-glycosylation remained endoglycosidase H-sensitive, indicating inhibited trimming.

Conclusions:

• The SARS-CoV M protein possesses a single N-glycosylation site at N4.
• Inhibition of N-linked sugar side chain trimming occurs during M protein maturation in SARS-CoV infected cells and virions.
• These findings provide insights into the post-translational modification and processing of the SARS-CoV M protein during viral assembly.