This is achieved by forming a protein shell around the nucleic acid. Virus assembly is a complex process that involves interactions with the viral genome, the viral structural proteins and for enveloped viruses a lipid membrane. The assembly mechanisms differ between virus families and are in most cases poorly understood. This thesis describes protein interactions involved in alphavirus assembly.
Alphaviruses are among the best-characterised enveloped viruses.
This is surrounded by a lipid bilayer derived from the host cell plasma membrane during budding. 80 spike complexes composed of three heterodimers of the envelope proteins, El and E2, traverse the membrane and interact with the nucleocapsid. The capsid protein has an autoprotease activity and cleaves itself from the growing polypeptide chain. Its enzymatic activity is special in that it only works in one reaction. The last Trp residue remains bound to the substrate pocket after cleavage and functions as a built in inhibitor.