Maturation of Viruses.

Viral genomes are transported between cells using various structural solutions such as spherical or filamentous protein cages, alone or in combination with lipid envelopes, in assemblies of varying complexity. Morphogenesis of the new infectious particles (virions) encompasses capsid assembly from individual components (proteins, and membranes when required), genome packaging, and maturation. This final step is crucial for full infectivity. During maturation, structural and physical changes prepare the viral particles for delivering their genome into cells at the right time and location. The virion must be stabilized for travel across harsh extracellular conditions, while enabling disassembly for genome exposure to replication and translation machineries. That is, maturation has to produce metastable particles. Common maturation strategies include structural reordering, controlled proteolysis, or posttranslational modifications. Here we outline the maturation process in representative members of the six realms proposed by the latest virus taxonomic classification.