Structural Biology/Biochemistry Seminar
Tuesday November 19, 2013
Kasha Laboratory, Room 112
11:15 AM

“The Pros and Cons of β-Sheet Formation: Insights from Solid-state NMR”

Dr. Anant Paravastu

Assistant Professor, Chemical & Biomedical Engineering
Faculty, Molecular Biophysics Graduate Program
Florida State University

http://www.eng.fsu.edu/cbe/people/paravastu.html

Formation of β-sheets is an important driving force for self-assembly of proteins and peptides into nanostructured materials. Although often associated with pathological nanostructures (e.g., neurotoxic amyloid fibrils and oligomeric species), designer peptides that self-assemble into amyloid-like structures have shown promise for regenerative therapies (e.g., neuron healing and stem cell approaches). As such, understanding β-sheet mediated self-assembly is of broad scientific interest.  In order to predict the complex biological effects of self-assembled peptides, we must first characterize key structural differences and assembly behaviors of different molecular states.

I will discuss our application of solid-state NMR spectroscopy to structural studies of three β-sheet forming self-assembling systems.  NMR strategies for structural characterization are based on probing of conformation-dependent chemical shifts and nuclear magnetic dipole-dipole couplings, complemented by computer simulations of molecular structure and nuclear spin dynamics.

System 1: We have produced stable samples of oligomeric 42-residue Alzheimer’s β-amyloid peptide.  NMR measurements indicate the oligomers are structurally distinguishable from fibrils formed by the same peptide, suggesting a molecular basis for higher oligomer toxicity.

System 2: We have used solid-state NMR to test proposed schemes for assembly of RADA16-I and MAX8, peptides that were rationally designed to self-assemble into nanofiber matrices.  Similarities and differences between structures proposed in the literature and NMR-based models illustrate the present level of predictability in peptide molecular design.

System 3: FGF-1 is a naturally occurring protein that adopts the three-fold symmetric β-trefoil architecture but lacks appreciable sequence symmetry. To investigate the interaction between sequence symmetry and protein folding, the laboratory of Michael Blaber (FSU College of Medicine) has engineered a purely symmetric protein from FGF-1, called “Symfoil.”  Symfoil, like FGF-1, folds into a β-trefoil; however, the aggregation propensity of Symfoil is greatly attenuated compared to FGF-1.  This result is in stark contrast to theoretical models of protein aggregation. We will use solid-state NMR data on self-assembled states of both FGF-1 and Symfoil-1 to motivate a possible explanation for this behavior.