8.A.251.  The Septin (Septin) Family 

Septins are in a highly conserved family of proteins that form palindromic hetero-oligomeric rods, which anneal into non-polar filaments. Via association with the plasma membrane, septin filaments recognize micron-scale membrane curvature, create diffusion barriers, and regulate cell morphogenic events via scaffolding other cytoskeletal polymers (i.e., filamentous actin [F-actin] and microtubules) and biochemical regulators of cell division, cell migration, and polarity establishment.  Three polybasic regions (PB1, PB2, and PB3) and an amphipathic helix (AH) are each sufficient for membrane interaction in vitro, and the AH domain has been implicated in conferring membrane curvature sensing in vivo in the filamentous fungus Ashbya (Meseroll et al. 2013).  An isoform of Caenorhabditis elegans septin UNC-61 is predicted to contain a TMS (Perry et al. 2025).  The TMS-containing sequence of a primate TMD-septin is sufficient for localization to cellular membranes (Perry et al. 2025).