Presenter(s): Patrick Connor
Faculty Mentor(s): Jeremy Anderson & Michael Harms
Poster 16
Session: Sciences
The human S100A9 protein is an important macromolecule found in large quantities in human neutrophils and at sites of inflammation. S100A9 has many functions including killing bacteria and turning on inflammation. It has been identified as a drug target to treat inflammatory disorders such as arthritis, but the mechanisms by which it achieves its diverse functions are poorly understood. In this study we investigated how S100A9 binds to two different types of targets as part of its biological function: 1) metals (which it sequesters to kill bacteria) and 2) innate immune receptors (which turn on inflammation). We measured binding interactions using isothermal titration calorimetry (ITC) and changes in protein structure using nuclear magnetic resonance spectroscopy (NMR). For the first project, we measured calcium and zinc binding to S100A9 by ITC and observed a large structural change in the protein by NMR. For the second project we measured binding of S100A9 to six peptides from the innate immune receptor TLR4. Only two peptides showed binding by ITC but three showed changes in structure by NMR indicating binding. We are further investigating where these peptides bind S100A9 by NMR. These studies show that S100A9 binds both calcium and zinc and that these metals bind cooperatively together. The peptide experiments showed that the peptides bind weakly to S100A9, which implies that binding may require a larger interface of TLR4. Determining how S100A9 performs these different functions is crucial to determining its role in disease states and what functions are involved.