Research

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

Daniel Voß^1,2 , Susanne Pfefferle³ , Christian Drosten^3,4 , Lea Stevermann¹ , Elisabetta Traggiai⁵ , Antonio Lanzavecchia⁵ and Stephan Becker¹

¹  Institute of Virology, Philipps-University Marburg, 35043 Marburg, Germany

²  Robert Koch-Institute, 13353 Berlin, Germany

³  Clinical Virology, Bernhard-Nocht Institute for Tropical Medicine, 20359 Hamburg

⁴  University of Bonn Medical Centre, Institute of Virology, 53127 Bonn German, Germany

⁵  Institute for Research in Biomedicine, CH 6500 Bellinzona, Switzerland

author email corresponding author email

Virology Journal 2009, 6:79doi:10.1186/1743-422X-6-79

Published:	18 June 2009

Abstract

The glycosylated membrane protein M of the severe acute respiratory syndrome associated coronavirus (SARS-CoV) is the main structural component of the virion and mediates assembly and budding of viral particles. The membrane topology of SARS-CoV M and the functional significance of its N-glycosylation are not completely understood as is its interaction with the surface glycoprotein S. Using biochemical and immunofluorescence analyses we found that M consists of a short glycosylated N-terminal ectodomain, three transmembrane segments and a long, immunogenic C-terminal endodomain. Although the N-glycosylation site of M seems to be highly conserved between group 1 and 3 coronaviruses, studies using a recombinant SARS-CoV expressing a glycosylation-deficient M revealed that N-glycosylation of M neither influence the shape of the virions nor their infectivity in cell culture. Further functional analysis of truncated M proteins showed that the N-terminal 134 amino acids comprising the three transmembrane domains are sufficient to mediate accumulation of M in the Golgi complex and to enforce recruitment of the viral spike protein S to the sites of virus assembly and budding in the ERGIC.