Bacteria fight off viruses with a protein like one of ours - Ars Technica

Mammals have a family of immune proteins called STAND (for reasons that are unimportant) that are part of what calls the innate immune system.

The STAND proteins all have a similar structure: a portion that recognizes pathogens, a portion that binds to a molecule that provides energy called ATP, and a portion that allows the protein to trigger a response.

The researchers showed that adding additional copies of the STAND genes to bacteria allowed them to resist viral infection more effectively.

Some of the STAND proteins recognized a key component of the virus's coat, killing the cell; others recognized the motor that packs the DNA inside the virus.

They then checked the equivalent proteins from a diverse range of related viruses and showed that the STAND proteins could recognize most of them.

So this suggests the STAND proteins recognize the shape of the structure, allowing them to defend against a huge range of viruses.

Further work showed that, once the viral protein was recognized, the STAND proteins aggregated in groups of four.

Looking through bacterial and archaeal genomes, approximately 5 percent of them have some form of STAND protein in them.

The researchers also did a check for viral genes that encode proteins that get in the way of the STAND proteins.

So, even when viral genes would normally induce STAND to kill cells, these STAND inhibitors allowed the cells to continue growing.

The other big remaining question is how STAND proteins became part of the immune response in such a huge range of organisms.

If you make a tree of STAND proteins based on how related they are, it doesn't line up with the tree of organisms in which they're found.

Put differently, if you look for the STAND protein most closely related to the one in E.