Wiktor Koźmiński's NMR group

Biological and Chemical Research Centre, University of Warsaw

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Wiktor Koźmiński's NMR Group

Congratulations!

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Congratulations to Saurabh Saxena on defending Ph.D. thesis entitled New NMR experiments for nucleic acids and intrinsically disordered proteins.

 

New Article in Scientific Reports

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Metal-coupled folding as the driving force for the extreme stability of Rad50 zinc hook dimer assembly

Tomasz Kochańczyk, Michał Nowakowski, Dominika Wojewska, Andrzej Ejchart, Wiktor Koźmiński, Artur Krężel


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The binding of metal ions at the interface of protein complexes presents a unique and poorly understood mechanism of molecular assembly. A remarkable example is the Rad50 zinc hook domain, which is highly conserved and facilitates the Zn2+-mediated homodimerization of Rad50 proteins. Here, we present a detailed analysis of the structural and thermodynamic effects governing the formation and stability (logK12 = 20.74) of this evolutionarily conserved protein assembly. We have dissected the determinants of the stability contributed by the small β-hairpin of the domain surrounding the zinc binding motif and the coiled-coiled regions using peptides of various lengths from 4 to 45 amino acid residues, alanine substitutions and peptide bond-to-ester perturbations. In the studied series of peptides, an >650 000-fold increase of the formation constant of the dimeric complex arises from favorable enthalpy because of the increased acidity of the cysteine thiols in metal-free form and the structural properties of the dimer. The dependence of the enthalpy on the domain fragment length is partially compensated by the entropic penalty of domain folding, indicating enthalpy-entropy compensation. This study facilitates understanding of the metal-mediated protein-protein interactions in which the metal ion is critical for the tight association of protein subunits.

 

A to B Transition

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'A' state

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Transition state

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'B' state

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New Article in Journal of Biomolecular NMR

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Five and four dimensional experiments for robust backbone resonance assignment of large intrinsically disordered proteins: application to Tau3x protein

Szymon Żerko, Piotr Byrski, Paweł Włodarczyk-Pruszyński, Michał Górka, Karin Ledolter, Eliezer Masliah, Robert Konrat, Wiktor Koźmiński


5Ds

New experiments dedicated for large IDPs backbone resonance assignment are presented. The most distinctive feature of all described techniques is the employment of MOCCA-XY16 mixing sequences to obtain effective magnetization transfers between carbonyl carbon backbone nuclei. The proposed 4 and 5 dimensional experiments provide a high dispersion of obtained signals making them suitable for use in the case of large IDPs (application to 354 a. a. residues of Tau protein 3x isoform is presented) as well as provide both forward and backward connectivities. What is more, connecting short chains interrupted with proline residues is also possible. All the experiments employ non-uniform sampling.

 

New Article in Journal of Biomolecular NMR

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Amino acid recognition for automatic resonance assignment of intrinsically disordered proteins

Alessandro Piai, Leonardo Gonnelli, Isabella C. Felli, Roberta Pierattelli, Krzysztof Kazimierczuk, Katarzyna Grudziąż, Wiktor Koźmiński, Anna Zawadzka-Kazimierczuk


amino selective

Resonance assignment is a prerequisite for almost any NMR-based study of proteins. It can be very challenging in some cases, however, due to the nature of the protein under investigation. This is the case with intrinsically disordered proteins, for example, whose NMR spectra suffer from low chemical shifts dispersion and generally low resolution. For these systems, sequence specific assignment is highly time-consuming, so the prospect of using automatic strategies for their assignment is very attractive. In this article we present a new version of the automatic assignment program TSAR dedicated to intrinsically disordered proteins. In particular, we demonstrate how the automatic procedure can be improved by incorporating methods for amino acid recognition and information on chemical shifts in selected amino acids. The approach was tested in silico on 16 disordered proteins and experimentally on α-synuclein, with remarkably good results.

 


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