Disease-associated polyglutamine stretches in monomeric huntingtin adopt a compact structure.

Abnormal polyglutamine (polyQ) tracts are the only common feature in nine proteins that each cause a dominant neurodegenerative disorder. In Huntington's disease, tracts longer than 36 glutamines in the protein huntingtin (htt) cause degeneration. In situ, monoclonal antibody 3B5H10 binds to different htt fragments in neurons in proportion to their toxicity.

Identifying polyglutamine protein species in situ that best predict neurodegeneration.

Polyglutamine (polyQ) stretches exceeding a threshold length confer a toxic function to proteins that contain them and cause at least nine neurological disorders. The basis for this toxicity threshold is unclear. Although polyQ expansions render proteins prone to aggregate into inclusion bodies, this may be a neuronal coping response to more toxic forms of polyQ.

Apolipoprotein E expression and purification.

Since the discovery of the association of apolipoprotein E (apoE) 4 with Alzheimer's disease 17 years ago, numerous in vitro experiments with the apoE isoforms (apoE2, apoE3, and apoE4) have been performed to try to understand the basis for this association. The majority of these studies used commercial sources for apoE, but some used recombinant protein. In either case, these studies were most often conducted without considering the ramifications of the structural and biophysical differences among the three isoforms or without adequate quality control of the preparations.

An optimized negative-staining protocol of electron microscopy for apoE4 POPC lipoprotein.

Apolipoprotein E (apoE), one of the major protein components of lipoproteins in the peripheral and central nervous systems, regulates cholesterol metabolism through its interaction with members of the low density lipoprotein receptor family. One key to understanding apoE function is determining the structure of lipid-bound forms of apoE. Negative-staining (NS) electron microscopy (EM) is an easy and rapid approach for studying the structure and morphology of lipid-bound forms of apoE.

Insight on the molecular envelope of lipid-bound apolipoprotein E from electron paramagnetic resonance spectroscopy.

Although a high-resolution X-ray structure for the N-terminal domain of apolipoprotein E (apoE) in the lipid-free state has been solved, our knowledge of the structure of full-length apoE in a lipid-bound state is limited to an X-ray model fitting a molecular envelope at 10-A resolution. To add molecular detail to the molecular envelope, we used cysteine mutagenesis to incorporate spin labels for analysis with electron paramagnetic resonance (EPR) spectroscopy. Twelve cysteine residues were introduced singly and in pairs at unique locations throughout apoE4 and labeled with an EPR spin probe.