About the Seminar:

Title:

Solid State NMR Characterization of Low Complexity Protein Sequence Assembly Mechanisms

Abstract:

Proteins harboring low complexity amino acid sequences form organized and condensed assemblies functionally and pathologically in living cells. Assembly is driven by weak and transient molecular interactions, however, how these interactions collectively produce condensed assemblies in specific biological contexts is not well characterized. Our current efforts focus on condensation mechanisms involving β-strand mediated hydrogen bond interactions, which illustrate the power of solid state NMR to address the properties of these ubiquitous protein domains. Amino acid sequence degeneracy is a significant challenge for the analysis of NMR spectra. Therefore, assignment of the resonances observed in solid state NMR spectra of assemblies formed by low complexity protein domains is not routine. We have solved this problem for the fibrils formed by the low complexity domains of several RNA-binding proteins and an intermediate filament protein. Our approach uses a computational algorithm to obtain statistically significant and unambiguous assignments for the signals observed in 2D and 3D cross-polarization-based 13C-detected spectra to determine the structurally rigid segments of the low complexity sequences in the fibrils. These resonance assignments allow us to use solid state NMR to probe the assembly of low complexity domains in different environments. Our comparative analysis provides insight into the molecular mechanisms for how these protein domains assemble functionally and pathologically. We present our results for the TDP43 RNA-binding protein that illustrate how characteristic alanine resonance patterns report on different structural motifs in different samples. We also present our newly published work using difference spectroscopy characterize the role of structural heterogeneity in the assembly of the TIA1 RNA binding protein. Finally, we present our results examining the role of intrinsically disordered regions in the assembly of non-canonical intermediate filaments.

About the Speaker:

Dylan T. Murray earned his Ph.D. in the Molecular Biophysics Graduate Program at Florida State University. Working under the direction of Dr. Timothy A. Cross at the National High Magnetic Field Laboratory, he developed solid state nuclear magnetic resonance methods to characterize integral membrane protein structures in native-like lipid bilayers. After that, he pursued postdoctoral training with Dr. Robert Tycko in the Lab of Chemical Physics at the National Institutes of Health. While there, he determined a molecular structure for a protein fibril formed by the FUS RNA-binding protein (PDB code 5W3N), also using solid state nuclear magnetic resonance. Additional postdoctoral projects included characterizing a molecular chaperone interacting with a protein fibril and the investigation of a disease mutation that increases pathological aggregation in muscular dystrophy. In July 2018, he joined the Chemistry Department at UC Davis as an Assistant Professor, part of a nuclear magnetic resonance faculty search.