Tubulin-Like Proteins in Prokaryotic DNA Positioning

Abstract

A family of tubulin-related proteins (TubZs) has been identified in prokaryotes as being important for the inheritance of virulence plasmids of several pathogenic Bacilli and also being implicated in the lysogenic life cycle of several bacteriophages. Cell biological studies and reconstitution experiments revealed that TubZs function as prokaryotic cytomotive filaments, providing one-dimensional motive forces. Plasmid-borne TubZ filaments most likely transport plasmid centromeric complexes by depolymerisation, pulling on the plasmid DNA, in vitro. In contrast, phage-borne TubZ (PhuZ) pushes bacteriophage particles (virions) to mid cell by filament growth. Structural studies by both crystallography and electron cryo-microscopy of multiple proteins, both from the plasmid partitioning sub-group and the bacteriophage virion centring group of TubZ homologues, allow a detailed consideration of the structural phylogeny of the group as a whole, while complete structures of both crystallographic protofilaments at high resolution and fully polymerised filaments at intermediate resolution by cryo-EM have revealed details of the polymerisation behaviour of both TubZ sub-groups.

Subcellular Organization: A Critical Feature of Bacterial Cell Replication

“…In rod-shaped bacteria, one way to ensure inheritance of a low-copy-number factor upon division is by segregating copies to opposite ends of the cell. This strategy is used by a subset of low-copy-number plasmids whose segregation mechanisms are based on active transport and dynamic cytoskeletal filaments made of distant actin or tubulin homologs (Fink and Aylett, 2017; Gayathri and Harne, 2017). This is illustrated by the ParM/R system encoded by the low-copy-number E. coli plasmid R1 (Moller-Jensen et al, 2003).…”