PEP-19 is an intrinsically disordered protein (IDP) that binds to the calcium signal regulating protein calmodulin and enhances its calcium ion binding kinetics. Alterations in PEP-19 expression have been associated with calcium signaling disruption. In the brain, PEP-19 has been shown to be protective against glutamate induced cytotoxicity. Its levels are decreased in the brain in Huntington’s disease, and its levels are increased in brain areas spared in Alzheimer’s disease, suggesting that PEP-19 is protective against calcium overload. PEP-19 over expression in mice leads to premature neuronal differentiation and learning deficits. This is particularly interesting as the gene for PEP-19 is found on chromosome 21, likely linking the aberrations caused by PEP-19 over expression to the learning and memory deficits of Down Syndrome. When bound to calmodulin, ~20 residues at PEP-19’s C-terminus become helical while the N-terminal half of the protein remains disordered. Consistent with the partial gain of helix when bound to calmodulin, PEP-19 belongs to a class of IDPs whose native conformational ensemble is predicted to change depending on the environment. We hypothesized that the conformational ensemble of PEP-19 can be influenced by its environment with the possible induction of secondary structure.We investigated this possibility by utilizing fluorescence resonance energy transfer (FRET) fluorimetry to determine PEP-19’s N- to C-terminal distance as a proxy for compaction and circular dichroism (CD) spectroscopy to determine secondary structure content of PEP-19. These experiments were performed both in the absence and presence of crowding agents, denaturants, calcium ions, and alterations in ionic strength in order to ascertain the effects of environment on PEP-19’s conformational ensemble. Additionally, we utilized analytical ultracentrifugation (AUC), size exclusion chromatography (SEC), and fluorescence anisotropy to investigate the interaction between calmodulin and PEP-19.<br/>

Investigation and perturbation of PEP-19's comformational ensemble

2019 Spring National Meeting

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