"Science" Zhang Feng's team discovered a new antiviral defense system in bacteria

Below is a press release from the Broad Institute of MIT and Harvard today

Bacteria use a variety of defense strategies to fight viral infections, some of which have led to breakthrough technologies such as CRISPR-based gene editing

One of these untapped microbial defense systems has been discovered and described by a team led by researchers at MIT's Broad Institute, Harvard University, and MIT's McGovern Institute for Brain Research

The study was published in the journal Science

"This work demonstrates the amazing unification of how pattern recognition occurs in different organisms," said senior author Feng Zhang

Microbial Armory

In an earlier study, researchers scanned the DNA sequence data of hundreds of thousands of bacteria and archaea and found thousands of genes that are characteristic of microbial defense

In humans and plants, STAND ATPase proteins fight infection by recognizing the pathogen itself or the pattern of cellular responses to infection

Next, the scientists wanted to know which part of the phage triggered the response, so they passed the viral genes to the bacteria one at a time

The discovery is astonishing and unprecedented

Scientists also discovered that these proteins function as endo-DNA enzymes that cut the bacteria's own DNA, killing the cell and thus limiting the further spread of the virus

Structural Analysis

To learn more about how microbial STAND ATPases detect viral proteins, the researchers used cryo-electron microscopy to examine their molecular structures when bound to viral proteins

The team found that entry or terminator proteins from viruses are embedded in a pocket of STANDATPase proteins, with each STAND ATPase protein grabbing a viral protein

Tetramers bind tightly to viral proteins from other phages, suggesting that STAND ATPase senses the three-dimensional shape of viral proteins, rather than their sequence

STAND ATPases in humans and plants also activate specific functions in cells by forming multiunit complexes