The Rapunzel virus has a strangely long tail, and we finally know why: ScienceAlert

Viruses and bacteria have been locked in an endless race for billions of years, and it has caused one predator to evolve into a “tail monster”.

A unique bacteria eater virusor bacteriophage, is officially called P74-26, although it is colloquially known as “Rapunzel”. virus.

Like the absurdly long locks of a fairy-tale princess, the pathogen’s “ponytail” stands out among its peers.

Almost a micrometer long, the appendage is 10 times longer than most other bacteriophages.

In fact, it has the longest tail of any known virus and, oddly enough, is also the most stable.

P74-26 tail compared to most other phage tails. (Agnello et al., Journal of Biological Chemistry, 2023)

According to a new study, this impressive appendage is probably what enables Rapunzel virus to find and pierce one of the most difficult bacteria on earth and in one of the most inhospitable environments.

In bubbling hot springs that reach temperatures well over 77 °C (170 °F), Rapunzel virus live by infecting the bacterium Thermus thermophilus and using another cell’s machinery for reproduction and reproduction.

By combining multiple images of the viral tail at different points in its construction, the researchers were able to decipher its unique structure. Computer simulations further elucidated the “highly entangled network of interactions” that coordinates this impressively long probe.

“We used a technique called a cryo-electron microscope, which is a huge microscope that allows us to take thousands of images and short movies at very high magnification,” explains microbiologist Emily Agnello of the University of Massachusetts (UMass) Chan Medical School.

“By taking lots of pictures of phage tail tubes and stacking them together, we were able to figure out exactly how the building blocks fit together.”

Bacteriophage tails come in different lengths and styles: some long, some flexible, some short, and some stiff. These molecular “machines” have evolved to recognize specific bacterial host cells before invading them and then deliver their genomes to the cytoplasm for replication.

Given the lock-and-key nature of this attack, there are many different types of bacteriophage tails and they are found in virtually every habitat on Earth. But how exactly do these tails differ?

So far, scientists have characterized very few phage-host interactions, and now that antibiotic resistance is a growing threat to human health, experts are turning to phages for ideas on how to defeat superbugs.

For example, Rapunzel virusThe tail appears to be such a threat to bacteria because its building blocks interlock and stack together.

Despite its large size virusAccording to the researchers, its tail has half as many building blocks as other bacteriophages, and that seems to play a decisive role.

“We think what has happened is something old virus fused its building blocks into a single protein,” says biochemist Brian Kelch of UMass.

“Imagine two small Lego blocks fused into one big brick with no seams. This long tail is built from larger, sturdier building blocks. We think it could stabilize the tail at high temperatures.”

Rapunzel viral image
Image of the Rapunzel virus. (Leonora Martinez-Nunez)

These very sturdy sub-units stack with a “ball and socket” type mechanism, reminiscent of Lego bricks, with studs on one side and a pocket on the other.

In viruses, each of these building blocks has a kind of ring-like shape, meaning that the entire tail forms a hollow tube when completed. This is the channel along which virus transmits its genome once it has invaded a bacterial cell.

“Our study finds that these building blocks can change shape or conformation when they come together,” says Agnello.

“This shape-changing behavior is important for the building blocks to fit together and form the correct structure in the anus.”

Rapunzel virus its tail is exceptionally long, which seems to give it extra strength when locking onto and penetrating bacteria. At the same time, however, the sheer length means that there is a greater chance that the tail assembly will go wrong.

The researchers believe there must be internal mechanisms that keep the developing tail on track, and these mechanisms are likely shared with other phages.

Understanding how they work could one day help researchers create better treatments against the deadly bacteria.

“I believe that studying unique, interesting things can lead to discoveries and applications that we can’t even imagine yet,” says Agnello.

Now that they know how virustail shapes, the researchers plan to genetically alter its length to see how that might change its interaction with bacteria.

Regardless of the outcome, these tests teach us something new.

The study was published Journal of Biological Chemistry.

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