| Cell membranes participate in multiple functions and define the frontiers of life itself. Erythrocytes have been used as a model to study membranes because of its relative simplicity. The beauty of the molecular microarchitecture of erythrocyte membrane skeleton has been correlated with their remarkable mechanical properties. The aim of this research is to understand the molecular basis of erythrocyte membrane skeleton biomechanics with a special emphasis on the junctional complexes.; Genetic and protein engineering was used to understand the molecular interaction between structural proteins in the junctional complex, specifically tropomyosin isoform 5 (TM5) and erythrocyte tropomodulin (E-Tmod), through the elucidation of their binding sites. Hydrophobic forces exerted by residues at positions “a” and “d”, and salt links between residues at positions “e” and “g” in heptad repeats of α-helices are found to be critical for TM5/E-Tmod binding.; Macroscopic biomechanical properties of mouse erythroid cells with the E-Tmod gene deleted were tested using a micropipette aspiration technique. The absence of this structural protein has important consequences on the viability of the mouse embryo and the mechanical strength of the erythroid membrane is weakened.; Finally, with the aim to correlate the molecular microarchitecture with the macroscopic biomechanical properties, a mesoscale model of the junctional complex was developed using the connectivity geometry of spectrin, actin protofilament and suspension complexes. Mechanical properties of modular unfolded spectrin derived from single molecule force spectroscopy were incorporated. The model simulated various conditions with physiological significance, such as equibiaxial extension, anisotropic extension, and spectrin damage to visualize the behavior of the actin protofilament and estimate the magnitude of the forces exerted on the structural elements in the junctional complex.; This research elucidated for the first time, corresponding binding sites of TM5 and E-Tmod, biomechanical properties on E-Tmod knock out erythroid cells, and a three-dimensional mesoscale model of the junctional complex. Increased knowledge of the erythrocyte membrane skeleton microarchitecture coupled with genetic engineering, single molecule force spectroscopy, and mathematical modeling, will open an emerging field in which a new generation of biomimetic smart membranes could be generated. |
