TitleNMR characterization of intrinsically disordered alpha-synuclein
NameWu, Kuen-Phon (author), Baum, Jean (chair), Levy, Ronald (internal member), Talaga, David (internal member), Nanda, Vikas (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectChemistry and Chemical Biology,
Parkinsons disease--Molecular aspects,
DescriptionA broad range of human diseases arise from the loss of the native function of a specific peptide or protein. The pathological conditions of these diseases are generally referred to as protein misfolding and aggregation problem. An increasing number of misfolded proteins are associated with the deposition of protein aggregation in the brain cells resulting in neurodegenerative diseases, for example, the aggregated α-synuclein (αSyn) in sporadic Parkinson’s disease.
αSyn is an intrinsically disordered protein and the aggregation kinetics are sensitive to the changes of amino acids and chemical environments. The structural conversion of αSyn from an unfolded monomeric ensemble to a well-ordered fibril remains unclear. In this work, nuclear magnetic resonance (NMR) was applied to characterize the aggregation-prone species including homologous mouse αSyn and human αSyn at low pH. Comparison of human and mouse αSyn at pH 7.4 and at supercooled aqueous solution presents a less compact mouse αSyn ensemble with transient inter-chain interactions at the N-terminal region. Characterization of αSyn conformational ensembles at both neutral and low pH shows that the altered charge distribution at low pH changes the structural properties of these ensembles and leads to rapid aggregation. Paramagnetic relaxation enhancement (PRE) experiments using mixed isotope (15N) and spin labeled αSyn further illustrate different intermolecular contacts of low-populated transient complex at neutral and low pH. A head-to-tail αSyn complex transiently stabilized by the electrostatic interactions at neutral pH is observed while a tail-to-tail αSyn complex via hydrophobic interactions at low pH is seen. This work provides novel structural insight into the molecular conversion of αSyn at the very early nucleation state.
In addition to understanding the aggregation mechanism of αSyn, an approach that deconvolutes the strong modulation of fast hydrogen exchange (HX) rates on the transverse relaxation rate (R2) of disordered proteins is also presented. This work shows an HX-free R2 profile of αSyn at pH 7.4 and provides an opportunity to understand NMR relaxation of disordered proteins or unstructured loop regions in folded proteins at fast HX conditions such as high pH or high temperature.
NoteIncludes bibliographical references (p. 153-165)
Noteby Kuen-Phon Wu
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.