scholarly journals Biophysical properties governing septin assembly

2021 ◽  
Author(s):  
Benjamin L Woods ◽  
Ian L Seim ◽  
Jessica Liu ◽  
Grace McLaughlin ◽  
Kevin S. Cannon ◽  
...  
Keyword(s):  
Physical Model ◽  
Yeast Extract ◽  
Cell Membranes ◽  
Regulatory Proteins ◽  
Biophysical Properties ◽  
Regulatory Mutants ◽  
Filament Assembly ◽  
Pure Protein ◽  
Crowded Environments ◽  
Septin Filament

Septin filaments build structures such as rings, lattices and gauzes that serve as platforms for localizing signaling and organizing cell membranes. How cells control the geometry of septin assemblies in poorly understood. We show here that septins are isodesmic polymers, in contrast to cooperative polymerization exhibited by F-actin and microtubules. We constructed a physical model to analyze and interpret how septin assemblies change in the presence of regulators in yeast extracts. Notably filaments differ in length and curvature in yeast extract compared to pure protein indicating cellular regulators modulate intrinsic biophysical features. Combining analysis of extracts from regulatory mutants with simulations, we found increased filament flexibility and reduced filament fragmentation promote assembly of septin rings, whereas reduced flexibility in crowded environments promotes local filament alignment. This work demonstrates how tuning of intrinsic features of septin filament assembly by regulatory proteins yields a diverse array of structures observed in cells.

scholarly journals Septin 9 has Two Polybasic Domains Critical to Septin Filament Assembly and Golgi Integrity

iScience ◽  
2020 ◽  
Vol 23 (5) ◽  
pp. 101042 ◽  
Author(s):  
Mohyeddine Omrane ◽  
Amanda Souza Camara ◽  
Cyntia Taveneau ◽  
Nassima Benzoubir ◽  
Thibault Tubiana ◽  
...  
Keyword(s):  
Septin 9 ◽  
Filament Assembly ◽  
Polybasic Domains ◽  
Septin Filament

scholarly journals Septin collar formation in budding yeast requires GTP binding and direct phosphorylation by the PAK, Cla4

2004 ◽  
Vol 164 (5) ◽  
pp. 701-715 ◽  
Author(s):  
Matthias Versele ◽  
Jeremy Thorner
Keyword(s):  
Wild Type ◽  
Gtp Hydrolysis ◽  
Filament Assembly ◽  
Gtp Binding ◽  
Type Mutant ◽  
Binding Residues ◽  
Septin Filament ◽  
Assembly Defect

Assembly at the mother–bud neck of a filamentous collar containing five septins (Cdc3, Cdc10, Cdc11, Cdc12, and Shs1) is necessary for proper morphogenesis and cytokinesis. We show that Cdc10 and Cdc12 possess GTPase activity and appropriate mutations in conserved nucleotide-binding residues abrogate GTP binding and/or hydrolysis in vitro. In vivo, mutants unable to bind GTP prevent septin collar formation, whereas mutants that block GTP hydrolysis do not. GTP binding-defective Cdc10 and Cdc12 form soluble heteromeric complexes with other septins both in yeast and in bacteria; yet, unlike wild-type, mutant complexes do not bind GTP and do not assemble into filaments in vitro. Absence of a p21-activated protein kinase (Cla4) perturbs septin collar formation. This defect is greatly exacerbated when combined with GTP binding-defective septins; conversely, the septin collar assembly defect of such mutants is suppressed efficiently by CLA4 overexpression. Cla4 interacts directly with and phosphorylates certain septins in vitro and in vivo. Thus, septin collar formation may correspond to septin filament assembly, and requires both GTP binding and Cla4-mediated phosphorylation of septins.

scholarly journals Control of septin filament flexibility and bundling

2017 ◽  
Author(s):  
Anum Khan ◽  
Jay Newby ◽  
Amy S. Gladfelter
Keyword(s):  
Physical Properties ◽  
Relative Proportion ◽  
Higher Order ◽  
Membrane Properties ◽  
Guanine Nucleotide ◽  
Filament Length ◽  
Cell Morphogenesis ◽  
Biophysical Properties ◽  
Nucleotide Hydrolysis ◽  
Septin Filament

AbstractSeptins self-assemble into heteromeric rods and filaments to act as scaffolds and modulate membrane properties. How cells tune the biophysical properties of septin filaments to control filament flexibility and length, and in turn the size, shape, and position of higher-order septin structures is not well understood. We examined how rod composition and nucleotide availability influence physical properties of septins such as annealing, fragmentation, bundling and bending. We found that septin complexes have symmetric termini, even when both Shs1 and Cdc11 are coexpressed. The relative proportion of Cdc11/Shs1 septin complexes controls the biophysical properties of filaments and influences the rate of annealing, fragmentation, and filament flexibility. Additionally, the presence and exchange of guanine nucleotide also alters filament length and bundling. An Shs1 mutant that is predicted to alter nucleotide hydrolysis has altered filament length and dynamics in cells and impacts cell morphogenesis. These data show that modulating filament properties through rod composition and nucleotide binding can control formation of septin assemblies that have distinct physical properties and functions.

scholarly journals CHO/LY‐B cell growth under limiting sphingolipid supply: Correlation between lipid composition and biophysical properties of sphingolipid‐restricted cell membranes

2021 ◽  
Vol 35 (6) ◽  
Author(s):  
Bingen G. Monasterio ◽  
Noemi Jiménez‐Rojo ◽  
Aritz B. García‐Arribas ◽  
Howard Riezman ◽  
Félix M. Goñi ◽  
...  
Keyword(s):  
Cell Growth ◽  
B Cell ◽  
Lipid Composition ◽  
Cell Membranes ◽  
Biophysical Properties

Pathological levels of glucosylceramide change the biophysical properties of artificial and cell membranes

2017 ◽  
Vol 19 (1) ◽  
pp. 340-346 ◽  
Author(s):  
Ana R. P. Varela ◽  
Ana E. Ventura ◽  
Ana C. Carreira ◽  
Aleksander Fedorov ◽  
Anthony H. Futerman ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Gaucher Disease ◽  
Cell Membranes ◽  
Cell Models ◽  
Biophysical Properties ◽  
Artificial Membranes ◽  
P Accumulation

Accumulation of glucosylceramide decreases membrane fluidity in artificial membranes and in cell models of Gaucher disease.

Aging and the biophysical properties of cell membranes

Life Sciences ◽  
1985 ◽  
Vol 37 (15) ◽  
pp. 1403-1409 ◽  
Author(s):  
Bruce M. Cohen ◽  
George S. Zubenko
Keyword(s):  
Cell Membranes ◽  
Biophysical Properties

scholarly journals Molecular recognition at septin interfaces: the switches hold the key

2020 ◽  
Author(s):  
Higor Vinícius Dias Rosa ◽  
Diego Antonio Leonardo ◽  
Gabriel Brognara ◽  
José Brandão-Neto ◽  
Humberto D’Muniz Pereira ◽  
...  
Keyword(s):  
High Resolution ◽  
Molecular Recognition ◽  
Crystal Structures ◽  
Molecular Level ◽  
Small Gtpases ◽  
Structural Basis ◽  
List Type ◽  
Filament Assembly ◽  
New Interactions ◽  
Septin Filament

ABSTRACTThe assembly of a septin filament requires that homologous monomers must distinguish between one another in establishing appropriate interfaces with their neighbours. To understand this phenomenon at the molecular level, we present the first four crystal structures of heterodimeric septin complexes. We describe in detail the two distinct types of G-interface present within the octameric particles which must polymerize to form filaments. These are formed between SEPT2 and SEPT6 and between SEPT7 and SEPT3, and their description permits an understanding of the structural basis for the selectivity necessary for correct filament assembly. By replacing SEPT6 by SEPT8 or SEPT11, it is possible to rationalize Kinoshita’s postulate which predicts the exchangeability of septins from within a subgroup. Switches I and II, which in classical small GTPases provide a mechanism for nucleotide-dependent conformational change, have been repurposed in septins to play a fundamental role in molecular recognition. Specifically, it is switch I which holds the key to discriminating between the two different G-interfaces. Moreover, residues which are characteristic for a given subgroup play subtle, but pivotal, roles in guaranteeing that the correct interfaces are formed.HIGHLIGHTSHigh resolution structures of septin heterodimeric complexes reveal new interactionsSwitches of small GTPases are repurposed in septins to play key roles in interface contactsThe GTP present in catalytically inactive septins participates in molecular recognitionConservation of interface residues allows for subunit exchangeability from within septin subgroupsSpecific residues for each septin subgroup provide selectivity for proper filament assemblyGRAPHICAL ABSTRACT

scholarly journals Study of Lipid Heterogeneity on Bilayer Membranes Using Molecular Dynamics Simulations

2021 ◽  
Author(s):  
G. Narahari Sastry ◽  
Nandan Kumar
Keyword(s):  
Molecular Dynamics ◽  
Human Cell ◽  
Cell Membranes ◽  
Theoretical Calculations ◽  
Structure And Function ◽  
Head Group ◽  
Membrane Thickness ◽  
Biophysical Properties ◽  
Dynamics Simulations ◽  
And Function

Abstract Human cell membranes consist of various lipids that are essential for their structure and function. Several experimental techniques have been used to characterize the composition of human cell membranes; however, it is challenging task to depict in theoretical calculations. In this work, we have investigated the structure-function relationship of lipids in both homogeneous and heterogeneous bilayer models using Molecular-Dynamics to delineate the effect of heterogeneity on the biophysical properties of membranes. Results illustrated that the biophysical properties of heterogeneous membranes are dependent on the lipid composition and concentration. We observed that the presence of cholesterol in combination with other lipids, introduced compactness of the membrane, increasing the membrane thickness. The density of lipid head group, phosphate, and glycerol-ester in presence of cholesterol with or without sphingomyelin is an underlying reason for membrane ordering. The radial distribution function shows that the cholesterol, sphingomyelin and phosphatidylethanolamine self-interaction and the interaction between cholesterol and phosphatidylethanolamine determine the structure and function of the heterogeneous membrane. Our findings provide a baseline for membrane heterogeneity that would help in understanding the physiological properties of membranes and may help to wisely select the heterogeneous bilayer model to mimic the realistic human cell membranes and the associated phenomenon.

scholarly journals Controlling septin filament flexibility and bundling

2017 ◽  
Author(s):  
Anum Khan ◽  
Jay Newby ◽  
Amy S Gladfelter
Keyword(s):  
Physical Properties ◽  
Relative Proportion ◽  
Higher Order ◽  
Membrane Properties ◽  
Guanine Nucleotide ◽  
Filament Length ◽  
Cell Morphogenesis ◽  
Biophysical Properties ◽  
Nucleotide Hydrolysis ◽  
Septin Filament

Septins self-assemble into heteromeric rods and filaments to act as scaffolds and modulate membrane properties. How cells tune the biophysical properties of septin filaments to control filament flexibility and length, and in turn the size, shape, and position of higher-order septin structures is not well understood. We examined how rod composition and nucleotide availability influence physical properties of septins such as annealing, fragmentation, bundling and bending. We found that septin complexes have symmetric termini, even when both Shs1 and Cdc11 are coexpressed. The relative proportion of Cdc11/Shs1 septin complexes controls the biophysical properties of filaments and influences the rate of annealing, fragmentation, and filament flexibility. Additionally, the presence and exchange of guanine nucleotide also alters filament length and bundling. An Shs1 mutant that is predicted to alter nucleotide hydrolysis has altered filament length and dynamics in cells and impacts cell morphogenesis. These data show that modulating filament properties through rod composition and nucleotide binding can control formation of septin assemblies that have distinct physical properties and functions.

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