Structural Changes of Forisomes at Surfaces upon Natural and Artificial Stimuli

• Applicants: Privatdozentin Dr. Gundula Noll; Professor Dr. Gunther Wittstock
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Structural Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550743680

Forisomes are mechanoproteins in plants, that respond to a change in Ca2+ ion concentration with a reversible change in shape and volume. Forisomes are huge protein complexes that assemble spontaneously from several subunits. The MtSEO-F1 subunit can be expressed biotechnologically in large quantities. These subunits form artificial forisomes that also respond to changes in Ca2+ ion concentration and also to changes in other ion concentrations. For a prospective use of artificial forisomes as biogenic switches, they have to be coupled to surfaces, where previous work showed that their behavior is not uniform. Before using such proteins technologically, the understanding of their switching behavior and their coupling to surfaces must be improved. In this project a new methodology shall be developed that allows to study the switching behavior of individual surface-bound artificial forisomes using a novel combination of infrared microscopy and scanning electrochemical microscopy (SECM). The MtSEO-F1 subunits form micrometer-sized protein complexes that can be resolved with both techniques. The change in length of the protein complexes is in the range of several micrometers. The two microscopies provide complementary information: Infrared microscopy provides information about the covalent and non-covalent binding motives in the different states of the protein complex and SECM is sensitive to the permeability of the protein complexes and thus provides information about the packing of secondary protein structures within artificial forisomes before and after a switching process. The use of microscopy enables the study of individual artificial forisomes and the assessment of variations in structure and responses between individual artificial forisomes. This methodology shall be used to study how artificial forisomes can be bound most effectively to electrode surfaces and how this self-assembly process can be controlled by chemical surface modification. Site directed mutagenesis of the MtSEO-F1 subunit will be used to study the influence of individual amino acids on the assembly process at artificial surfaces, the stability and the switching behavior. Furthermore, by varying the amino acid sequence and the chemical modification of the electrode surfaces, it will be investigated how the switching behavior can be adapted to non-physiological triggers such as changes in pH, electrical potentials of a contact electrode or changes in the concentration of other metal ions.

• DFG Programme: Research Grants
• Major Instrumentation: Infrarot-Mikroskop
• Instrumentation Group: 5040 Spezielle Mikroskope (außer 500-503)
• Co-Investigator: Privatdozentin Dr. Izabella Brand