Molecular mechanisms behind protein halo tolerance

• Applicant: Dr. Ana Vila Verde
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 382674566

Halophilic microorganisms have the unusual ability to thrive in conditions that would kill most other organisms: they live in salterns with NaCl concentrations as high as 4 M. To prevent high osmotic pressures that would rupture them, many halophiles accumulate KCl in they cytoplasm also up to molar concentrations. Halophilic proteins, with their extraordinary ability to remain functional at high salt concentrations, have thus enormous potential for biotechnology: they are indispensable for devices that can function in sea water, enabling, e.g., hydrogen production using dehydrogenases, or carbon capturing using carbonic anhydrases, without straining fresh water resources. Harnessing the potential of halophilic proteins requires that we understand the molecular mechanisms behind halophilicity: understanding these mechanisms is the topic of this proposal. The ability of proteins to remain functional at high salt concentrations correlates with their high content in negatively charged amino acids, and low content in amino acids with large hydrophobic groups. This proposal focuses on the least understood and most controversial aspect - the role of the negatively charged amino acids - which I will investigate using molecular dynamics simulations and atomistic models. By comparing halophilic proteins with their non-halophilic counterparts at different NaCl concentrations and, for smaller proteins, investigating both the folded state and the unfolded ensemble, I will identify how negatively charged surface amino acids determine halophilicity and I will quantify the contribution of these mechanisms to protein stability. I will specifically investigate hydrogenases and carbonic anhydrases, which are of particular interest for biotechnological applications. I will take advantage of recent algorithmic and hardware advances to perform microsecond long simulations and to adequately sample the folded and the unfolded protein ensembles. The significance of this proposal lies in the clarification of molecular mechanisms fundamental for our understanding of protein stability, and critical for the development of artificial enzymes and biomolecular devices that function in saline conditions.

• DFG Programme: Research Grants