Vitruvian HBV Capsid

Jodi Ann Hadden / Chemistry and Biochemistry / Post-Doc
Vitruvian HBV Capsid
Xray-crystallography, Computational modeling, Molecular dynamics simulation – Portrait
The hepatitis B virus (HBV) packages its genetic blueprint in a protein shell called a capsid. Like the capsids of other spherical viruses, the proteins that make up the HBV capsid are arranged according to icosahedral symmetry. The capsid depicted here is based on a computational model, in which theoretical methods have been used to fill in missing pieces of an experimental structure derived from X-ray crystallography. The Vitruvian HBV Capsid artwork celebrates the beauty of capsid architecture, the elegant mathematical relationships that describe capsid construction, and the incredible manner in which viruses leverage symmetry to reduce the number of different proteins they incorporate, and, thus, the size of the genetic blueprint they must encode. The constituent proteins of the HBV capsid can be considered as groups of five (pentamers) or six (hexmers). Eberhard’s theorem (upper right) indicates that a capsid must contain twelve pentamers to form a closed shell. The HBV capsid is composed of twelve pentamers and thirty hexamers (lower right). Pentamers (red) are located on icosahedral vertices, which are axes of fivefold symmetry. Hexamers are located on icosahedral edges, which are axes of twofold or quasi-sixfold symmetry. Three hexamers pack together on icosahedral faces, which are axes of threefold symmetry. The triangulation number T=4 of the capsid (upper left) describes the numerical and spatial relationship of pentamers and hexamers within the icosahedron, and also indicates that there are four unique positions that constituent proteins can occupy: A (red), B (beige), C (cyan), and D (blue). There are a total of T*60=240 proteins that make up the HBV capsid (lower left). These proteins are never found alone in nature, but always associate into dimers or capsids