![]() ![]() They speculated that a layer of resident filaments extends from the membrane that functions as a template for the filaments to polymerize and depolymerize on the cytosolic surface. speculated that the moving parts are arranged in a disorderly and random manner, whereas the ordered parts are static, but the photobleaching recovery experiment confirmed that the dynamic septin was also ordered. Whether the organization of mobile and immobile septins in higher-order structures is different in cells is still unknown. ![]() It has been proven that there is an exchange at the ring with free cytosolic septins. However, the resolution of the FPM is relatively low and only reveals the change in the direction of the septin protein and cannot distinguish specific structural changes.ĭifferent populations of mobile and immobile septins are present in cells. In addition, photobleaching fluorescence recovery experiments show that although the septin ring is rigid, the splitting septin ring is dynamic. These filaments are arranged parallel to the mother–bud axis in the ring, and are orthogonal to it in the double-ring state. The molecular rearrangement of highly ordered septin proteins during yeast cell division was observed by fluorescence polarization microscopy (FPM), accompanied by a 90° rotation of the septin filaments. Only living-cell imaging can reveal a dynamic process. Moreover, in vitro recombination imaging and EM imaging do not perfectly reveal the transformation process in the higher-order structures of septins during cell division. In complex organisms, distinguishing different substances and structures is generally based on structural characteristics, and distinguishing unstable structures is difficult. In EM imaging, the sample structure may change during preparation. The in vivo structure of septin is mainly imaged by EM through the septin ring of division cells. Although in vitro imaging has high accuracy and resolution, the reconstructed structures in vitro cannot completely represent the natural structure in vivo. ![]() In vitro imaging is used to obtain a segment or bundle of septin complexes by protein purification and recombination, then uses super-resolution or EM imaging to deduce its structure according to the results. The research methods for studying septin structures are mainly in vitro imaging technology and electron microscopy (EM). The process by which the septin filament controls the separation of the cell membrane between the mother and daughter cells is still not fully known. Before cytokinesis, the septin ring complex splits into two rings. After the bud appears, the septin complex at the bud neck expands into an hourglass shape. When yeast cells divide, septins first form a septin ring at the budding site. Seven genes have been identified in yeast, among which the four proteins Cdc3, Cdc10, Cdc11 and Cdc12 constitute the main part of the septin ring. Budding yeast is still a valuable model for the study of higher-order structures of septins, and its study may also apply to animal cells, helping to understand septin-related diseases. Filaments can be organized into various higher-order structures, such as linear arrays, filaments, rings and gauzes. Septins assemble into basic units these 17–32 nm rod-shaped non-polar hetero-oligomers are polymerized end-to-end into filaments. Septins exist in most eukaryotes and are conserved GTP-binding proteins that were first discovered to play a role in the cell cycle of budding yeast, S. ![]()
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