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Lecture

Alpha Helical Transmembrane Segments

In course

BIO-207: Cellular and molecular biology II

This course is aimed to familiarize students with the 3D organization of a eukaryotic cell, its compartmentalization, how cellular compartments communicate together and how a cell communicates with its environment. The related molecular mechanisms will be ...

Description

This lecture covers the structure of alpha helices in transmembrane proteins, focusing on their interaction with lipids and hydrophobicity. It explains the prediction of transmembrane regions using bioinformatics and the hydrophobicity index. The instructor discusses examples of transmembrane proteins and their asymmetric structures.

Instructors (3)

Françoise Gisou van der Goot Grunberg

Gisou van der Goot is the Head of the Laboratory of Cell and Membrane Biology, and founding member of the Global Health Institute (GHI), School of Life Sciences, at the Swiss Federal Institute of Technology Lausanne/EPFL (Ecole Polytechnique Fédérale de Lausanne). She is currently Vice President for Responsible Transformation, in charge of reinforcing values such as inclusion and sustainability throughout the School’s campus. From 2014 to 2020, she was Dean of the School of Life Sciences. Before joining EPFL, she was Group Leader at the Faculty of Sciences of the University of Geneva (UNIGE) and subsequently Associate Professor at the Faculty of Medicine of the same university. She studied engineering at the Ecole Centrale de Paris, then did a PhD in Molecular Biophysics at the Nuclear Energy Research Center, Saclay, France, followed by a postdoc at the European Molecular Biology Laboratory (EMBL) in Heidelberg. She obtained an EMBO Young Investigator award in 2001, a Howard Hughes International Scholar award in 2005 and the Swiss Prix Marcel Benoist in 2009, the same year she was elected EMBO member (European Molecular Biology Organisation). She is a leader in the fields of molecular and cellular understanding of bacterial toxins, the organization of mammalian membranes and in organelles biology. Professor van der Goot is member of diverse scientific boards such as the Swiss National Science Foundation (SNF), the Conseil suisse de la science et de la technologie (CSST) and the European Research Council (ERC).

Wouter Richard Karthaus

Romain Zufferey

Official source

Related concepts (31)

Transmembrane domain

A transmembrane domain (TMD) is a membrane-spanning protein domain. TMDs may consist of one or several alpha-helices or a transmembrane beta barrel. Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in TMDs are often hydrophobic, although proteins such as membrane pumps and ion channels can contain polar residues. TMDs vary greatly in size and hydrophobicity; they may adopt organelle-specific properties. Transmembrane domains are known to perform a variety of functions.

Transmembrane protein

A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently undergo significant conformational changes to move a substance through the membrane. They are usually highly hydrophobic and aggregate and precipitate in water. They require detergents or nonpolar solvents for extraction, although some of them (beta-barrels) can be also extracted using denaturing agents.

Lipid bilayer

The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus, and membranes of the membrane-bound organelles in the cell. The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be.

Lipid raft

The plasma membranes of cells contain combinations of glycosphingolipids, cholesterol and protein receptors organised in glycolipoprotein lipid microdomains termed lipid rafts. Their existence in cellular membranes remains somewhat controversial. It has been proposed that they are specialized membrane microdomains which compartmentalize cellular processes by serving as organising centers for the assembly of signaling molecules, allowing a closer interaction of protein receptors and their effectors to promote kinetically favorable interactions necessary for the signal transduction.

Hydrophobe

In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.

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