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Septins are a group of GTP-binding proteins found primarily in eukaryotic cells of fungi and animals, but also in some green algae. Different septins form protein complexes with each other. These complexes can further assemble into filaments, rings and gauzes. Assembled as such, septins function in cells by localizing other proteins, either by providing a scaffold to which proteins can attach, or by preventing diffusion of molecules from one compartment of the cell to another.〔〔 Septins have been implicated in the localization of cellular processes at the site of cell division, at the plasma membrane, at sites where specialized structures like cilia or flagella are attached to the cell body.〔 In yeast cells, they compartmentalize parts of the cell and build scaffolding to provide structural support during cell division at the septum, from which they derive their name.〔 Recent research in human cells suggests that septins build cages around bacterial pathogens, immobilizing the harmful microbes and preventing them from invading other cells. As filament forming proteins, septins can be considered part of the cytoskeleton.〔 Apart from forming non-polar filaments, septins associate with cell membranes, actin filaments and microtubules.〔 Although present in most eukaryotes, septins have not been observed in plants.〔 ==Structure== Septins are P-Loop-NTPase proteins that range in weight from 30-65 kDa. Septins are highly conserved between different eukaryotic species. They are composed of a variable-length proline rich N-terminus with a basic phosphoinositide binding motif important for membrane association, a GTP-binding domain, a highly conserved Septin Unique Element domain, and a C-terminal extension including a coiled coil domain of varying length.〔 Septins interact either via their respective GTP-binding domains, or via both their N- and C-termini. Different organisms express a different number of septins, and from those symmetric oligomeres are formed. For example, in humans Sept7-Sept6-Sept2-Sept2-Sept6-Sept7 form one complex, and in yeast Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 form another one. These complexes then associate to form non-polar filaments, filament bundles, cages or ring structures in cells.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「septin」の詳細全文を読む スポンサード リンク
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