How a phage enzyme rewires nearly every protein in its bacterial host

Within minutes of a bacteriophage called T7 infecting E. coli, a single viral enzyme — a kinase the team calls T7K — does something almost absurd in its scope: it attaches a phosphate group to nearly every protein in the bacterial cell. EMBL Heidelberg scientists report in Nature on 19 August 2026 that this phosphorylation sweep is not a side effect of infection but the infection itself proceeding, and that the kinase preferentially targets the DNA-binding proteins at the heart of the bacterium’s immune defenses.

The paper, led by Dario Bartolec and colleagues, frames T7K as a “loose cannon”: an enzyme with little apparent substrate selectivity that fires phosphate groups onto whatever it encounters. Nature’s own research briefing on the work summarizes the team’s central finding — that T7K phosphorylates nearly all bacterial proteins, but specifically goes after DNA-binding proteins that form the core of nucleic-acid-targeting defense systems, effectively shorting them out. A typical bacterial cell has on the order of a couple of thousand distinct protein species; the kinase modifies almost all of them within minutes.

That sounds wasteful. It probably is. But the strategy works because the defenses T7 is trying to neutralize — systems that recognize foreign DNA, that cut it, that sound alarms — happen to be drawn overwhelmingly from the same pool of DNA-binding proteins the kinase already saturates. Independent science-press coverage of the EMBL study describes the kinase’s “shutoff domain” as the part that tilts the enzyme toward these defense proteins specifically, ensuring that the very proteins the bacterium needs to recognize and resist T7 are the first ones taken offline. The shotgun approach is doing something narrower than it looks.

There is a real puzzle in the older literature, though, and the new paper is also where it gets resolved. The EMBL release notes that earlier studies found deleting T7 kinase had little apparent effect on T7 infection in standard lab E. coli strains. That result sat uncomfortably with the kinase being conserved across T7 isolates for no reason. The Nature briefing explains why: lab strains have been engineered over decades to be easy to work with, and in the process they have shed most of their defense systems. With few defenses left to neutralize, the kinase becomes dispensable. The picture changes completely when T7 is tested against natural E. coli strains still carrying their full complement of DNA-binding immune systems — there, the kinase is essential for the phage to establish infection. The apparent riddle dissolves once you remember what lab strains actually are.

The result also has practical implications. Phage therapy — using viruses to treat bacterial infections, especially those resistant to antibiotics — depends on phages being able to overcome the defenses of whatever strain they encounter in a patient. A single phage deploying a single enzyme to disable an entire class of defenses at once is exactly the kind of broad, hard-to-evade-against strategy that clinical phage use needs. The EMBL release and its associated coverage both point toward engineering applications: understanding which phages carry kinase-based disarmament, and which defense systems are most vulnerable to it, opens a path to designing phage cocktails that are reliably effective against strains whose defenses would otherwise defeat them.

What is most striking about the finding, on the science side, is how much it reframes what “host takeover” looks like at the molecular level. The classical picture of phage infection involves a few well-targeted attacks: shut down the host’s transcription, degrade its chromosome, neutralize one or two specific defenses. T7K instead does something closer to carpet bombing, then lets selection — its own slight bias toward DNA-binding substrates — determine which bombs actually matter. It is the kind of mechanism that makes more sense once you see it as a single enzyme trying to win a war against an entire bacterial immune repertoire, rather than as a delicate piece of molecular surgery. The fact that it works, and works within minutes, is the part the EMBL team is now trying to understand in more detail.

Sources

• A viral ‘loose cannon’ enzyme helps phages shut down bacterial defences — European Molecular Biology Laboratory (EMBL)
• Virus deploys a ‘loose cannon’ enzyme to overpower bacterial defences — Nature (research briefing)
• Scientists Discover a “Loose Cannon” Virus Enzyme That Rewires Nearly Every Protein in a Bacterial Cell — SciTechDaily