A structural analysis of M protein in coronavirus assembly and morphology

Neuman, B. W., Kiss, G., Kunding, A. H., Bhella, D., Baksh, M. F. ORCID: https://orcid.org/0000-0003-3107-8815, Connelly, S., Droese, B., Klaus, J. P., Makino, S., Sawicki, S. G., Siddell, S. G., Stamou, D. G., Wilson, I. A., Kuhn, P. and Buchmeier, M. J. (2011) A structural analysis of M protein in coronavirus assembly and morphology. Journal of Structural Biology, 174 (1). pp. 11-22. ISSN 1047-8477 doi: 10.1016/j.jsb.2010.11.021

Abstract/Summary

The M protein of coronavirus plays a central role in virus assembly, turning cellular membranes into workshops where virus and host factors come together to make new virus particles. We investigated how M structure and organization is related to virus shape and size using cryo-electron microscopy, tomography and statistical analysis. We present evidence that suggests M can adopt two conformations and that membrane curvature is regulated by one M conformer. Elongated M protein is associated with rigidity, clusters of spikes and a relatively narrow range of membrane curvature. In contrast, compact M protein is associated with flexibility and low spike density. Analysis of several types of virus-like particles and virions revealed that S protein, N protein and genomic RNA each help to regulate virion size and variation, presumably through interactions with M. These findings provide insight into how M protein functions to promote virus assembly.