New Views of Phage Tail Assembly and Disassembly

Title: "New Views of Phage Tail Assembly and Disassembly"

Professor Alan R DAVIDSON, Department of Molecular Genetics, University of Toronto, Canada

Abstract:

Phage tails are complicated, multifunctional nanomachines. They mediate specific attachment of phage particles to the cell surface, penetration of the cell envelope, and delivery of the genome to the cell interior. Non-contractile tails, such as those of E. coli phage lambda, are composed of many copies of 7 to 10 different proteins that polymerize into a tube more than 100 nm in length. Successful assembly of this intricate structure occurs through multiple defined and regulated steps, many of which remain mysterious. The first half of this talk will describe a newly discovered role for a conserved family of deubiquitinases that is required for tail assembly of phage lambda and a large number of related phages. The second half of this talk will focus on a non-contractile-tail related entity called the F-type pyocin. Although closely related by protein sequence to phage tails like lambda, F-type pyocins are produced by strains of P. aeruginosa, and are used as weapons to kill strains of the same species. A high resolution structural view of the cell binding and penetration process of the F-type pyocin will be presented. This process involves a remarkable protein fold-switching phenomenon where a 160 residue region of the cell surface binding protein converts from an trimeric -helical coiled-coil to a trimeric -prism structure, composed only of  -strands. We show that this fold switch likely occurs in diverse phages and highlight the conserved sequence features of these proteins that allow one sequence to encode two completely different folds.

Invited by Paulo Tavares (paulo.tavares@i2bc.paris-saclay.fr)