| Summary: | In this work, we studied three proteins from three different organisms by EPR spectroscopy: NpHtrII is part of the phototaxis system found in halophilic archaea, ChR2 is a cation-selective channel isolated from a green alga, and HsaCCA is an enzyme involved in the protein biosynthesis of humans. The goal was to identify characteristic conformations and dynamics in each of the studied proteins that were linked to their specific functions. The scientific disciplines employed in this work include biochemistry (site-directed spin-labeling), bioinformatics (data analysis, molecular modeling), informatics (device control, software development), molecular biology (mutagenesis, transformation, heterologous protein expression, protein purification, protein characterization), and physics (EPR spectroscopy, optical spectroscopy, experimental assembly).
The experimental results show a strong interdependence between protein structure, conformers, dynamics, and function. Hydrogen bonds, although being a transient electrostatic attraction between polar molecules, are the key molecular interactions required for the conservation of protein functionality: Hydrogen bond networks in NpSRII and ChR2 stabilize the helix bundles, and hydrogen bond networks in HsaCCA mediate interdomain flexibility. However, the resulting structural alterations observed in our proteins manifest on a much larger scale: We have detected changes in the protein backbone mobility of the HAMP2 domain in NpHtrII after signaling.
We have discovered the TMH B movement in ChR2 accompanying channel opening. And we have documented a substrate-dependent motion of the head domain in HsaCCA during catalysis.
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