Dr. Johnson is a biochemist who studies how bacteria - particularly pathogens - respond to metals in their environment.

Dr. Johnson has an undergraduate degree from Duke University. He received his Ph.D. from the University of North Carolina, Chapel Hill, and completed postdoctoral work at St. Jude Children’s Research Hospital. He joined the faculty at the University of Arizona in 2016.

Copper is extremely toxic to many bacteria, including pathogens, and is actually used by the immune system to fight off infection. To deal with this, many bacteria have systems to get rid of copper. These systems are often made up of three parts:

1. a sensor protein that recognizes copper,
2. a chaperone protein that isolates the copper, and
3. an exporter protein that removes the copper from the cell.

The levels of all three proteins are repressed by the binding of the sensor to the DNA.

In a 2017 study, Dr. Johnson studied this system in Streptococcus pneumoniae, the bacteria that causes pneumonia. In addition to the fact that this is a medically relevant bacteria, Dr. Johnson was interested in the fact that the copper sensor and chaperone proteins in S. pneumoniae are unusual compared to the ones in other bacteria where this system has been studied in detail.

He found that the sensor protein can interact with two different metals: copper and zinc. While the sensor is interacting with zinc, it binds well to the DNA, keeping the levels of all three proteins low. When copper levels increase, copper out-competes zinc to interact with the sensor. This causes the sensor to release the DNA and increase the levels of the copper chaperone and copper exporter proteins. He also found that the chaperone was capable of altering the chemical state of the copper to make it more compatible with the exporter protein.

The ability of S. pneumoniae to get rid of copper helps it survive against the immune system trying to kill it. By better understanding how this works, we can design drugs that block this system and improve the chances of successfully fighting off the infection.