Current Research Highlights

Dynamic force spectroscopy: To get insights into the single molecule mechanics of the most prominent component of the M-band, the modular protein myomesin was expressed in-vitro in the group of J.C. Perriard (ETHZ, www.cell.biol.ethz.ch/) and was investigated on molecular scale using various methods (Circular Dichroism, Transmission Electron Microscopy and SPM). Imaging of single molecules was performed at the Maurice Müller Institute of the Biocenter (Group of U. Aebi) and mechanical manipulation was done at the Institute of Physics by dynamic force spectroscopy in our group (1, 8, 9). Figure 3 shows the sequential unfolding of protein monomers and the corresponding force vs. distance experimental data.

Figure 3: Dynamic force spectroscopy on myomesin muscle protein. The protein is cloned as a multimer and expressed in E.coli. The individual protein subunits are grafted onto an interface (gold or glass) and subjected to an external force. Individual sub-units unfold one by one by pulling with a atomic force cantilever in a physiological environment. Upper graph: Unfolding single subunits by pulling. Lower graph: Force versus distance plot. In collaboration with ETHZ (Group Perriard)

Our studies revealed that sarcomeric M-band component myomesin is an adaptable molecular spring. The Ig and Fn-like domains of myomesin demonstrate the high mechanical stability, comparable with the one of Ig-like domains of titin. The EH-myomesin isoform, expressed in some muscle types contains additional EH-fragment, shows no folding in EM and acts as an entropic spring similar the PEVK domain of titin in our pulling experiments. Providing extra elasticity for the M-bands might be necessary during embryonic heart development, but could also be adaptation to pathogenic circumstances in adults.

Again, an interdisciplinary collaborative effort was the key point to the completion of the project.