proIAPP is an Active Participant in its Own Correct Processing and Cleavage

Amylin is a 37-amino acid peptide hormone that is expressed as a prohormone, proamylin, alongside proinsulin in the islets of Langerhans in beta-cells. When working as it should, amylin helps maintain metabolic homeostasis, but when it is misfolds, amylin and its processing intermediates generate insoluble aggregates that form amyloid plaques on beta-cells, a clinical hallmark of type II diabetes mellitus. This thesis includes published work that introduced the first structure of pro-islet amyloid polypeptide bound to a fos-choline-12 micelle and discusses the membrane topology of this intrinsically disordered protein at the micelle-solvent interface. In the following chapter, we discuss structural differences exhibited by proamylin in mimetic environments that it samples during its maturation along the regulated secretory pathway. During this process, proamylin is acted upon by many different proteases, and samples a wide range of pH and membrane compositions. The conformational changes due to changes in pH and membrane charge were shown to protect a non-canonical cleavage site in the prohormone sequence. Cleavage at this site would yield a misprocessed, and potentially biologically inactive amylin, and the structured c-terminal prohormone segment of proamylin protects this site. In the final chapter, we briefly demonstrate the application of Intersection of Non-redundant Information on Resonance groups (INIR) to drastically improve spectral resolution. INIR uses an interleaved heteronuclear combination quantum coherence (HCQC) pulse program that collects information on the single-, zero- and double- quantum transitions. It simulates a higher resolution spectrum with our spectral fitting reconstruction software. We generated a 900-MHz spectrum of alpha-synuclein from 500-MHz with INIR and demonstrated that the spectra were comparable, and even surpassed, in some cases, the resolution of a 900-MHz equipped with a cryogenic probe.