Structure of the rabies virus: Spatial relationships of the proteins G, M 1, M 2 and N

Abstract

Summary The localization and spatial arrangement of the major structural proteins in rabies virions have been investigated through proteases and bivalent cross-linked effects on purified particles and subsequent analysis. Trypsin only removes the glycoprotein component from native virions, leaving small polypeptide fragments firmly anchored on spikeless particles, as analysed by acrylamide gel electrophoresis. On the other hand, tryptic hydrolysis of particles with membrane impaired by osmotic shock and EDTA treatment, releases G and then M2 proteins. In the same experimental conditions, M1 was shown to be roughly as resistant as N, suggesting, M1 is located in an inner position when compared to M2. Analysis of rabies virus cross-linked by the cleavable dithiobis(succinimidyl)propionate (DTBSP) revealed six major polymers ranging from 50 to 200 kd. They were identified as GN, GM1 and GM2 heterodimers and M22, G2 and G3 homopolymers, using two-dimensional SDS-PAGE analysis. In addition, the authors could not find NM1 heterocomplexes small enough to penetrate the running gel nor they could clearly identify N homopolymers. The detection of G2 and G3 complexes supports the idea that the surface projections are trimers rather than the G molecules are randomly distributed on the membrane. Moreover, the presence of GN, GM1 and GM2 heteropolymers reinforces the concept that the glycoprotein is a transmembrane protein, able to interact with the membrane protein M2, but also with the inner viral components of the nucleocapsid, M1 and N.