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K-State Today

April 17, 2018

Piotr E. Marszalek featured speaker for April 18 Biochemistry and Molecular Biophysics Seminar

By Biochemistry and Molecular Biophysics

Piotr E. Marszalek, professor of mechanical engineering and materials science at Duke Univeristy, will present "Mechanical unfolding, misfolding and refolding of multidomain proteins by single-molecule Atomic Force Spectroscopy and computer simulations" at 4 p.m. Wednesday, April 18, in 120 Ackert Hall as part of the Biochemistry and Molecular Biophysics Seminar series.

Marszalek received his graduate education in Poland. He received his doctorate from Electrotechnical Institute and his masters from the University of Warsaw. His research specialties include nanomaterial manufacturing and characterization, nanoscale/microscale computing systems, materials, nanoscience, and polymer and protein engineering.

Presentation abstract: In single-molecule force spectroscopy, or SMFS, individual proteins are mechanically stretched and relaxed in isolation from their neighbors, greatly reducing their opportunities to aggregate in their unfolded state. Thus, this technique is ideal for studying unfolding and refolding behavior of large proteins. Using Atomic Force Microscopy-based SFMS, steered molecular dynamics, or SMD, simulations along with protein engineering/truncations and denaturation approaches we examined the mechanical unfolding behavior of a number of large polypeptides such as ankyrin repeat proteins — up to 800 amino acids — phosphoglycerate kinase — PGK, 416 aa — and the firefly luciferase — Fluc, 550 amino acids. Generally, under mechanical conditions we capture complex sequential unfolding reactions that do not follow a simple two-state (N/U) model. In some cases — e.g. ankyrin repeats — SMFS approaches allow us to monitor directly and in real time the course of refolding reactions that also proceed stepwise. By combining SMFS experiments and coarse-grained MD/SMD simulations we were able to map unfolding, refolding and misfolding pathways for Fluc that explain its propensity to fold co-translationally. Taken together all these AFM mechanical studies augmented by SMD simulations suggest also a novel mechanism for the chaperone action on misfolded Fluc that we propose involves providing the protein with optimal co-translational-like conditions for its successful folding.

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