Salmonella search

UWL graduating senior helps get to the biological root of foodborne illness with protein discovery

From left, UWL Senior Damien Rasmussen and UWL Assistant Professor John May, along with other student researchers have discovered a novel protein found in Salmonella during an infection. Understanding its function could help researchers learn how to better treat Salmonella.

It was early spring 2016 when UWL Senior Damien Rasmussen knocked on Assistant Professor John May’s door looking for an undergraduate research experience. He’d just taken a biochemistry course the previous semester that got him interested in learning more — about the building blocks of life.

“There is something about a living system and seeing its complexity at the most fundamental level — how it comes together so intricately,” explains Rasmussen. “It amazes me.”

Now one of May’s research students, Rasmussen is face-to-face with that biological intricacy every day. On a Thursday afternoon, he sits at a computer monitor in May’s lab piecing together the 3D structure of the protein that no one has ever seen before.

May, Rasmussen and other student researchers in May’s lab discovered the structure of a protein produced by Salmonella during an infection. Rasmussen presented on the structure of the novel protein at the annual meeting of the American Society for Biochemistry and Molecular Biology on April 22-26 in Chicago.

The 3D structure of the protein will eventually be published in a peer-reviewed journal and be made available for researchers and educators around the world to look at in an international database of protein structures, the Protein Data Bank.

Discovering what a protein looks like is a critical first step to determining its function which May and his student researchers are now studying. Their research will ultimately contribute to scientific understanding of how to stop Salmonella, a bacterium that invades the intestinal tract causing about one million cases of foodborne illness in the U.S. each year.

‘A giant 3D puzzle’

UWL Senior Damien Rasmussen compares his research on the novel protein’s structure to assembling a giant 3D puzzle made up of hundreds of pieces.

Rasmussen compares his research on this protein’s structure to assembling a giant 3D puzzle made up of hundreds of pieces. Each piece of the protein puzzle is an amino acid — an assembly of atoms including carbon, oxygen, nitrogen, hydrogen and sulfur. The arrangement of those amino acids determines how the protein will fold in space and ultimately how it functions. Rasmussen’s puzzle building is guided by a 3D map on the computer screen that shows him the location of all of the atoms in the protein based on the position of their electrons.

Creating that electron map was no small task. It involved collaborating with a UWL colleague, Basu Bhattacharyya, associate lecturer of chemistry and biochemistry, and months of growing tiny crystals in May’s lab.

Rasmussen perseveres to grow crystals

Last summer, Rasmussen came into the lab each morning and peered under the microscope into hundreds of tiny muffin-tin like trays filled with water and salt solution. He and May were trying to find the perfect conditions to grow protein crystals.

Because an individual protein molecule is too small to see and analyze, even under a microscope, a special process called crystallization is used to obtain trillions of protein molecules in a symmetrical and repeating pattern. Then, a powerful x-ray machine can be used to recreate the 3D shape of the structure. But getting those first crystals to grow from a protein molecule isn’t easy.

Each summer morning Rasmussen looked for a crystal, he’d find nothing. He would modify the conditions and try again. Until one day in June after about 150 trials, Rasmussen spotted a tiny crystal. About five times the width of a human hair – and looking like a miniature snowflake — he spent the summer replicating those conditions to make more under May and Bhattacharyya’s guidance.

“It is exciting to see students take ownership of a project and to engage in the process of discovery,” says May.

But Rasmussen and May weren’t certain whether they were growing protein crystals or salt crystals until they took a road trip to the Advanced Photon Source at Argonne National Laboratory, a federally-funded research lab near Chicago that had the equipment to take an x-ray image of the crystalized protein. The x-ray yielded a complex pattern which they could immediately distinguish as a protein.

“That was the most exciting moment,” recalls Rasmussen. “We saw all these dots show up on the screen and we knew it was not salt, but a protein.”

It was a novel protein — no one had ever seen the structure of before. UWL structural biologist Basu Bhattacharyya was able to analyze the x-ray pattern and produce the electron map that May and Rasmussen used to create a 3D image of the protein’s structure.

That difficult and sometimes tedious process from crystallization to developing a 3D protein picture is what Rasmussen describes as “fun.” It’s helped him solidify that this type of biological scientific research is exactly what he’d like to do in life.

Rasmussen graduate during UWL’s spring commencement ceremony Sunday, May 14. He will begin the doctoral program in biochemistry, molecular biology, and biophysics at University of Minnesota in the fall. He says the more he understands about how life works at the molecular level, the more unbelievable it becomes, and the more motivated he is to continue studying it.

He ultimately would like to run his own laboratory some day in industry or academia.

“I’ve had a lot of jobs growing up where you have to wake up early and go to work. That can be tough. But I love to wake up and come to the lab and try to figure things out,” he says. “Yes, it can be tedious at times, but there is so much out there that people don’t know. There is always the possibility that you could be the one to uncover something new.”

And now, Rasmussen hopes he has helped discover a protein that could be important for understanding Salmonella infection. Eventually, that discovery could lead to better drugs that may someday save a person’s life.

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Strong support

Rasmussen became a McNair Scholar during his fourth year at UWL, which he says has been a “tremendous help” in his pursuit of graduate school. “From campus visits to help with the application process, the resources and insight they have provided me have been amazing,” he says. “The people involved with the program genuinely care about your success and are willing to do whatever they can to help you reach your goals.”

Rasmussen file

  • Gertrude Salzer Gordon Summer Research Fellow – Gundersen Health Systems (2015)
  • Biochemistry outstanding student of the year (2016)
  • Analytical outstanding student of the year (2017)

Research support

UWL Assistant Professor John May’s research is funded by UWL faculty research grants. May is grateful for collaborators at UW-Madison and UW-La Crosse who’ve been essential to the discovery process and provided valuable resources, including connection to a national research lab.