Type III-B CRISPR-Cas cascade of proteolytic cleavages. (https://pubmed.ncbi.nlm.nih.gov/38301007/)

These scientists wanted to understand how a specific type of immune system in bacteria works. This immune system is called CRISPR-Cas. They studied a type of CRISPR-Cas system found in a bacterium called Haliangium ochraceum.

They discovered that this system has two special proteins called SAVED-CHAT and PCaspase. These proteins are similar to something called caspase, which is found in our bodies and helps with cell processes.

The scientists found that when a molecule called cyclic tri-adenosine monophosphate (AMP) is present, it causes SAVED-CHAT to stick together and become active. When SAVED-CHAT is active, it can cut and activate the PCaspase protein.

Once PCaspase is activated, it starts cutting many other proteins in the bacterium. This cutting process interferes with the bacterium's normal functions and helps protect it from viruses.

In summary, the scientists discovered how this type of CRISPR-Cas system in bacteria detects and responds to a specific molecule, which then starts a chain reaction of protein cutting. This helps the bacteria defend itself against viruses.

Steens JA., Bravo JPK., Salazar CRP., Yildiz C., Amieiro AM., Kostlbacher S., Prinsen SHP., Andres AS., Patinios C., Bardis A., Barendregt A., Scheltema RA., Ettema TJG., van der Oost J., Taylor DW., Staals RHJ. Type III-B CRISPR-Cas cascade of proteolytic cleavages. Science. 2024 Feb 2;383(6682):512-519. doi: 10.1126/science.adk0378. Epub 2024 Feb 1.