Septin assemblies form by diffusion-driven annealing on membranes
Bridges, Andrew A.
Mehta, Shalin B.
Gladfelter, Amy S.
MetadataShow full item record
Septins assemble into filaments and higher-order structures that act as scaffolds for diverse cell functions including cytokinesis, cell polarity, and membrane remodeling. Despite their conserved role in cell organization, little is known about how septin filaments elongate and are knit together into higher-order assemblies. Using fluorescence correlation spectroscopy (FCS), we determined that cytosolic septins are in small complexes suggesting that septin filaments are not formed in the cytosol. When the plasma membrane of live cells is monitored by total internal reflection fluorescence (TIRF) microscopy, we see that septin complexes of variable size diffuse in two dimensions. Diffusing septin complexes collide and make end-on associations to form elongated filaments and higher-order structures, an assembly process we call annealing. Septin assembly by annealing can be reconstituted in vitro on supported lipid bilayers with purified septin complexes. Using the reconstitution assay, we show that septin filaments are highly flexible, grow only from free filament ends and do not exchange subunits in the middle of filaments. This work shows for the first time that annealing is an intrinsic property of septins in the presence of membranes and demonstrates that cells exploit this mechanism to build large septin assemblies.
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 111 (2014): 2146-2151, doi:10.1073/pnas.1314138111.
Showing items related by title, author, creator and subject.
Exploring the distribution and physiological roles of bacterial membrane lipids in the marine environment Saenz, James P. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-06)Lipids have a legacy in the geologic record extending back to the Archaean. Since the phylogenetic diversity of life is reflected in the structural diversity of biomolecules, lipid biomarkers that are shown to be diagnostic ...
Shanklin, D. Radford (2011-04-10)Pulmonary fibrosis implies antecedent lung injury which may or may not include inflammatory responses of the ordinary sort. The onset of breathing at mammalian birth is a different kind of lung injury, one occasioned by ...
Phosphorus supply drives rapid turnover of membrane phospholipids in the diatom Thalassiosira pseudonana Martin, Patrick; Van Mooy, Benjamin A. S.; Heithoff, Abigail; Dyhrman, Sonya T. (2010-11)In low phosphorus (P) marine systems phytoplankton replace membrane phospholipids with non-phosphorus lipids, but it is not known how rapidly this substitution occurs. Here, when cells of the model diatom Thalassiosira ...