Studies on membrane topology, N-glycosylation and functionality of SARS-CoV membrane protein

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• The severe acute respiratory syndrome-associated coronavirus (SARS-CoV) membrane protein M is crucial for viral particle assembly and budding.
• Understanding SARS-CoV M's membrane topology, N-glycosylation, and interaction with spike protein S is incomplete.

Purpose of the Study:

• To elucidate the membrane topology and functional significance of SARS-CoV M's N-glycosylation.
• To investigate the role of M in viral assembly and its interaction with spike protein S.

Main Methods:

• Biochemical analyses
• Immunofluorescence analyses
• Studies using recombinant SARS-CoV expressing glycosylation-deficient M
• Functional analysis of truncated M proteins

Main Results:

• SARS-CoV M possesses a short N-terminal ectodomain, three transmembrane segments, and a long C-terminal endodomain.
• N-glycosylation of M does not affect virion shape or infectivity.
• The N-terminal 134 amino acids of M are sufficient for Golgi localization and recruitment of spike protein S to ERGIC for virus assembly.

Conclusions:

• SARS-CoV M's N-terminal transmembrane domains are critical for its function in viral assembly and budding.
• N-glycosylation of SARS-CoV M is dispensable for virion formation and infectivity.
• The M protein's transmembrane region drives the recruitment of spike protein S for efficient virus production.