StrucShare Meeting:

Klemens Leo McJarrow Keller

Title: Resolving the tail structures of jumbophage PCH45

Abstract:

Chimalliviridae is a family of so-called 'jumbophages', tailed phages with a genome size of over 200kbp. They have been studied for their sophisticated mechanisms to evade host immunity, such as the formation of a nucleus-like shell during infection in which replication of the phage genome takes place. Until recently, the large size of the virions has made determining their structures to near-atomic resolution prohibitive. I will summarise my ongoing work in determining the contractile tail architecture of Serratia phage PCH45, a member of Chimalliviridae originally isolated from wastewater in Dunedin, New Zealand. In particular, I will focus on the strategies tried (successful and otherwise) in managing the size, complexity, and flexibility of these particles.

Daniel Gutierrez Del Rio

Title: Architecture of the haloarchaeal lemon-shaped virus His1 and of its tubular form.

Abstract:

Lemon-shaped viruses assemble pleomorphic virions that can elongate into tubular particles. This morphological variability limits the attainable resolution of cryo-EM single-particle analysis. To overcome this, we used walking alignment and local classification (WALC) to resolve the lemon and tubular forms of Halovirus His1 (Salterprovirus australiense). The virion comprises six structural proteins arranged into seven strands coiling around the genome. Two distinct structures cap each end: a tail with associated lipids and a crown sealed by a plug. In this talk, I will show how tight aromatic contacts within each strand, together with weak aliphatic interactions between strands result in flexible virions suited to extreme salinity environments.