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Disputation Michail Lazaratos

30.11.2022 | 16:30
Thema der Dissertation:
The role of dynamic hydrogen bond networks in protonation coupled dynamics of retinal proteins
Abstract: Hydrogen bonds are an essential interaction in membrane proteins. Embedded in complex hydrated lipid bilayers, intramolecular interactions through the means of hydrogen bonding networks are often crucial for the function of the protein. Internal water molecules that occupy stable sites inside the protein, or water molecules that visit transiently from the bulk, play an important role in shaping local conformational dynamics forming complex networks that bridge regions of the protein via water-mediated hydrogen bonds that can function as wires for the transferring of protons as a part of the protein’s function. The membrane-embedded channelrhodopsins which are found in archaea, are proteins that couple light induced isomerization of the retinal chromophore with proton transfer reactions and passive flow of cations through their pore. The photocycle of channelrhodopsins begins with absorption and isomerization of the retinal from an all-trans state to a 13-cis state and followed by the deprotonation of the Schiff base. Analyses of long Molecular Dynamics trajectories of channelrhodopsin variants embedded in hydrated lipid membranes and large data sets of static structures were performed to detect and dissect dynamic hydrogen-bond networks. Through the use of 2-dimensional graphs of the protein hydrogen bond networks, protein groups potentially important for the proton transfer activity were identified. Local dynamics are highly affected by point mutations of amino acids important for function. The interior of channelrhodopsin C1C2 hosts extensive networks of protein and hydrogen bonded-water molecules, and a network that can bridge transiently the two retinal chromophores in the dimer.

Zeit & Ort

30.11.2022 | 16:30

Hörsaal A (1.3.14)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)