Nature's favorite building block: Deciphering folding and capsid assembly of proteins with the HK97-fold

• Published in: Virology (New York, N.Y.) N.Y.), 2015-05, Vol.479-480, p.487-497
• Main Authors: Suhanovsky, Margaret M, Teschke, Carolyn M
• Format: Article
• Language: English
• Subjects: Archaeal Viruses - physiology; Bacteriophages - physiology; Capsid Proteins - chemistry; Capsid Proteins - metabolism; Herpesviridae - physiology; Protein Folding; Protein Multimerization; Virus Assembly
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2015.02.055

For many (if not all) bacterial and archaeal tailed viruses and eukaryotic Herpesvirdae the HK97-fold serves as the major architectural element in icosahedral capsid formation while still enabling the conformational flexibility required during assembly and maturation. Auxiliary proteins or Δ-domains strictly control assembly of multiple, identical, HK97-like subunits into procapsids with specific icosahedral symmetries, rather than aberrant non-icosahedral structures. Procapsids are precursor structures that mature into capsids in a process involving release of auxiliary proteins (or cleavage of Δ-domains), dsDNA packaging, and conformational rearrangement of the HK97-like subunits. Some coat proteins built on the ubiquitous HK97-fold also have accessory domains or loops that impart specific functions, such as increased monomer, procapsid, or capsid stability. In this review, we analyze the numerous HK97-like coat protein structures that are emerging in the literature (over 40 at time of writing) by comparing their topology, additional domains, and their assembly and misassembly reactions.