The Stringent Response Inhibits DNA Replication Initiation in E. coli by Modulating Supercoiling of .

The stringent response enables bacteria to respond to a variety of environmental stresses, especially various forms of nutrient limitation. During the stringent response, the cell produces large quantities of the nucleotide alarmone ppGpp, which modulates many aspects of cell physiology, including reprogramming transcription, blocking protein translation, and inhibiting new rounds of DNA replication. The mechanism by which ppGpp inhibits DNA replication initiation in remains unclear.

A bacteriophage tubulin harnesses dynamic instability to center DNA in infected cells.

Dynamic instability, polarity, and spatiotemporal organization are hallmarks of the microtubule cytoskeleton that allow formation of complex structures such as the eukaryotic spindle. No similar structure has been identified in prokaryotes. The bacteriophage-encoded tubulin PhuZ is required to position DNA at mid-cell, without which infectivity is compromised.

The structure and assembly mechanism of a novel three-stranded tubulin filament that centers phage DNA.

Tubulins are a universally conserved protein superfamily that carry out diverse biological roles by assembling filaments with very different architectures. The underlying basis of this structural diversity is poorly understood. Here, we determine a 7.

A phage tubulin assembles dynamic filaments by an atypical mechanism to center viral DNA within the host cell.

Tubulins are essential for the reproduction of many eukaryotic viruses, but historically, bacteriophage were assumed not to require a cytoskeleton. Here, we identify a tubulin-like protein, PhuZ, from bacteriophage 201φ2-1 and show that it forms filaments in vivo and in vitro. The PhuZ structure has a conserved tubulin fold, with an unusual, extended C terminus that we demonstrate to be critical for polymerization in vitro and in vivo.