Provided; Elizabeth Nelson
Provided; Elizabeth Nelson

Moonlighting Proteins

by KeShonna Jackson ’24

Bacteria, viruses, and other microscopic organisms are undetectable to the human eye, but they are everywhere. They live within us, sometimes harmfully and sometimes not, and can affect us in ways we do not always understand.

Brianna Johnson ’21 has had her own battles with these microscopic organisms. She has found her passion in trying to understand their impacts and intricacies.

“Growing up, I had all these infectious diseases, like Lyme disease and pneumonia, and it was personally interesting to think about how those diseases worked and why they were attacking my body,” Johnson says. “I think infectious diseases in general show a lot of societal inequalities, so it's important to increase our understanding to try to combat the inequalities that they engender.”

Since the fall of her sophomore year, Johnson has been working in the lab of Tobias Doerr, Microbiology. The Doerr lab focuses on cell wall biology, a branch of microbiology that revolves around the supportive and protective structure of the cell. Johnson’s specific research is an offshoot of a project by her mentor Shannon Murphy, a PhD candidate. Murphy was researching the ability of the cell wall to resist attack by antibiotics, and a certain aspect of Murphy’s work caught Johnson’s attention.

“One of the questions [Shannon] raised but didn’t have much time to follow up on interested me. [Researchers] had seen this influence from an important protein, AroK. The last major paper written about it was in 1996. The authors found that [AroK] has a weird connection to the cell wall, but we still don't really know what it is. The idea that a protein can have multiple physiologically distinct functions I think is often overlooked in biology,” Johnson says.

Known Proteins, Unexplored Functions

AroK is an essential metabolic protein. Its primary role is to serve as a fuel source, assisting in processes that help regulate the cell’s energy inputs and outputs. Johnson's experiments affirmed AroK's surprising connection to the cell wall and revealed yet another role for AroK. The protein seems to help maintain cell wall homeostasis, another regulating process that maintains the cell’s shape and ensures that its contents are secure.

“Seeing that AroK is somehow implicated in the homeostatic process was interesting because its normal function as a metabolic protein isn't related to homeostasis at all,” Johnson says.

“The last major paper written about it was in 1996. The authors found that [AroK] has a weird connection to the cell wall, but we still don't really know what it is.”

Johnson hopes that by building on this idea of multifunctional proteins and their unseen importance, her research will bring their impact to light. “I think we grossly underestimate the amount of proteins with multiple functions. I don’t think we need to start looking out for new things, but for multiple functions in proteins that we already know exist.”

The Benefit of Obstacles

Johnson’s success as a researcher comes from her desire to take control of her own work. She can take a question and run with it, and she has the support of her colleagues in the lab.

“Shannon has mentored me all the way through, and now I am much more independent,” Johnson says. “Everyone in the lab, their willingness to help me learn and pursue my own independent project, got me to do so much more than I ever imagined I could do.”

Yet Johnson’s research on the AroK protein was not without challenges. To see exactly what AroK interacts with, Johnson intended to tag it. In the attempt, she discovered a major obstacle: AroK is too small to be tagged. The setback forced her to take an entirely different approach. Johnson instead had to mutate the protein—a structural rather than functional method of experimentation. Although at the time this complication was frustrating for Johnson, looking back, she recognizes its benefits.

“It exposed me to a whole different side of biology that I've never done before. My honors thesis focused on the structural work more than I ever imagined it could. It let me learn something new,” she says.

Unexpected Results

“One of the biggest things I learned is that an experiment never goes as planned. You're always going to need to troubleshoot and have a backup plan. You have to be able to critically look at what you did and see where that may have gone wrong and think about how to tackle the question from a different angle,” Johnson says.

Johnson typically spends her time in the lab as an engineer, restructuring the gene sequences of bacteria in order to get them to express the AroK protein, then measuring the growth of the bacteria over time to determine AroK’s impact. When Johnson studied the effect of AroK on pathogenic Escherichia coli and Vibrio cholerae bacteria, she arrived at some interesting results.

Her research revealed that when AroK is absent in E. coli, the bacteria are more resistant to antibiotic attack. When AroK is absent in the bacteria that cause cholera disease, V. cholerae, the opposite is true. The bacteria are actually more susceptible to antibiotic attack. Johnson finds this strange, as E. coli and V. cholerae are thought to be similar in behavior.

“We didn't expect it at all because E. coli. and V. cholerae are fairly closely related pathogens. So, it was really interesting to see these opposite effects taking place. It might suggest a fundamental difference in these two closely related organisms that isn’t well documented,” Johnson says.

Made for the Lab

Johnson knows the lab is where she is meant to be. Being so involved with research as an undergrad has only affirmed her passion for lab work and microbiology. She is grateful for her time in the Doerr lab, and for all the people she has met at Cornell.

“That’s the thing I'm going to miss the most, you know, the people. To be able to see and work with my friends on a daily basis. All of that is just incredible. Also, just being able to meet a ton of new people who have my same interests and people who don't. I'm going to miss it so much.”

After graduating, Johnson, a Biological Sciences major, is going to work in a microbiology research lab at Rockefeller University. Although she will miss Cornell, she feels prepared to take on her next step.

“I know there will be a learning curve, but I think given all the experience that I've gained over the past four years that I have the skills to learn everything and pick it up quickly. I'm really excited.”