STUDIES ON THE MORPHOLOGY OF ALPHAVIRUSES

The symmetrical arrangement of subunits in envelope and nucleocapsid of alphaviruses (Sindbis and Semliki Forest) was investigated. The 80 subunits of the envelope display a hexon-penton clustering in a T = 4 icosahedral surface lattice. The glycoprotein projections are located in bundles on the surface of the morphological subunits. The nucleocapsids of alphaviruses appear to be composed of 32 capsomers arranged in a T + 3 surface lattice. Based on electron micrographs of alphaviruses and their nucleocapsids a model was constructed with a T = 3 nucleocapsid and a T = 4 envelope showing that it is possible to have a direct contact between envelope and capsid proteins in spite of different triangulation numbers. © 1979.