Determining how a protein folds is one of the most difficult problems in biochemistry. One class of proteins are membrane bound proteins. Because a membrane is a difficult environment this class of proteins poses unique challenges to studying their structure. One of the methods that can be used to determine a protein’s folding conformation is EPR spectroscopy. In EPR spectroscopy we can use the information about radical species to help determine structural information. In this we can use labels with radical species and probe the unpaired electrons local environment to determine structural information about the protein. Using EPR, this study focused on a specific class of membrane bound proteins known as pinholins. These proteins form small holes on a bacteria’s cell membrane allowing for the completion of a bacteriophages life cycle. One of these proteins, known as Pinholin S21, contains 2 domains, and has an active and inactive conformation. How these domains are embedded into a membrane, can be described by their helical tilt angle. This information helps define how these 2 domains are oriented in the membrane. With EPR spectroscopy we were able to find the helical tilt angles for the 2 major structures of this molecule, TMD1 and TMD2, to be 84 degrees and 15.7 degrees respectively. This information helps further refine the previously developed model for pinholin, and offers new methods for using EPR spectroscopy to investigate membrane bound proteins. Using methods such as this could allow more complicated protein structures to be solved, allowing for future discoveries such as drug development for human illnesses of misfolding proteins.
Author: Andrew Daufel, Biochemistry Major
Faculty Advisor: Gary Lorigan, Chemistry and Biochemistry
Graduate Student Advisors: Rasal Khan and Indra Sahu, Chemistry and Biochemistry
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