NSF Award
0094577
Burnett, Roger M.<br/>MCB-0094577<br/><br/><br/>We will explore the principles by which viruses are constructed from their constituent proteins, and advance ways of imaging very large biological structures at high resolution. The molecular structures of two very large virions will be obtained by combining two independent imaging methods. Cryo-electron microscopy (EM) will yield three-dimensional reconstructions of adenovirus and bacteriophage PRD1, and their mutants. Difference imaging will use the known X-ray structures of the two major coat proteins with the EM reconstructions to define the molecular envelopes and locations of proteins at the vertex and others acting as capsid "cement."<br/><br/>We want to understand the molecular interactions determining the architecture and stability of adenovirus and bacteriophage PRD1, and to develop our hypothesis that they have evolved from a common ancestor. How can two dsDNA viruses have large pseudo T=25 virions with quite different sizes, although they are formed from similar major coat proteins? Both proteins have double "viral barrel" subunits to give trimers with pseudo-hexagonal shapes that can closely pack. How are these and other similarities, such as in DNA organization and replication, maintained while the viruses have evolved? They infect very different hosts, and PRD1 has an unusual internal membrane. The role and evolution of cementing proteins will be studied by imaging viral mutants. These proteins are important in large macromolecular assemblies as they resolve the conflicting requirements for weak interactions to ensure accurate assembly of major components, and the strong bonding necessary for stability.
