Correct and efficient capsid assembly typically requires the presence of a scaffolding protein, which can be encoded as a standalone protein or as a fusion with the maturation protease or the MCP the scaffolding protein/domain is subsequently cleaved by the maturation protease and the fragments are removed from the capsid (Dokland, 1999). The portal, as the name implies, also serves as a conduit through which the viral DNA is packaged into and released from the capsid during virus entry (Dedeo et al., 2019 Newcomb et al., 2005 Tavares, 2018). This review will focus on the viral scaffolding proteins, for which an increasing amount of structural and functional information has recently become available. In viruses, scaffolding proteins are found both in the form of internal cores and external bracing, and may form elaborate and complex structures. They may also work to ensure the fidelity of the assembly process by preventing the formation of improper interactions, in many ways similar to the role of molecular chaperones in protein folding. Scaffolding proteins may act in a specific fashion, by actively encouraging the formation of correct protein-protein interactions, or more generally by nucleating and promoting assembly. Scaffolding proteins have been described primarily from viral systems, in particular from the double-stranded DNA bacteriophages, but most likely play a more general role in macromolecular assembly, a fundamental process in all biological systems.

They associate specifically with the nascent protein complex during assembly, but are subsequently removed, and are absent from the mature structure. Scaffolding proteins are proteins that are required to catalyse, regulate or modulate some step in the assembly of a macromolecular complex.

Protein scaffold definition