Amphipathic

These examples are programmatically amphipathic from various online sources to illustrate current usage of the word 'amphipathic. Send us feedback about these examples. Accessed 4 Mar, amphipathic. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Federal government websites often end in. The site is secure. Small molecules that reconstitute the binding mode s of a protein and in doing so elicit a programmed functional response offer considerable advantages in the control of complex biological processes. The development challenges of such molecules are significant, however. Many protein-protein interactions require multiple points of contact over relatively large surface areas. More significantly, several binding modes can be superimposed upon a single sequence within a protein, and a true small molecule replacement must be pre-programmed for such multi-modal binding. This is the case for the transcriptional activation domain or TAD of transcriptional activators as these mofifs utilize a poorly characterized multi-partner binding profile in order to stimulate gene expression.

Amphipathic

Federal government websites often end in. The site is secure. Amphipathic helices AHs , a secondary feature found in many proteins, are defined by their structure and by the segregation of hydrophobic and polar residues between two faces of the helix. This segregation allows AHs to adsorb at polar—apolar interfaces such as the lipid surfaces of cellular organelles. Using various examples, we discuss here how variations within this general scheme impart membrane-interacting AHs with different interfacial properties. Among the key parameters are: i the size of hydrophobic residues and their density per helical turn; ii the nature, the charge, and the distribution of polar residues; and iii the length of the AH. Depending on how these parameters are tuned, AHs can deform lipid bilayers, sense membrane curvature, recognize specific lipids, coat lipid droplets, or protect membranes from stress. Via these diverse mechanisms, AHs play important roles in many cellular processes. They can be found in many stably folded proteins. However, in this review we will focus solely on AHs that fold in contact with the surface of a bilayer-bound organelle or a lipid droplet inside the cell [ 1 , 2 ]. Owing to this segregation, the helix lays down parallel to the membrane interface and anchors the protein in a reversible manner. Since the development of pioneering studies on amphipathic helical regions in apolipoproteins and secreted antimicrobial peptides [ 2 , 3 , 4 ], the field of AHs has flourished, with the discovery that many eukaryotic, viral, or bacterial proteins contain AHs which contribute to intracellular membrane targeting, sometimes in combination with other modes of protein—membrane interaction [ 2 , 5 ]. Furthermore, studies have revealed that many AHs act not only as membrane anchors but also fulfill other functions owing to their extended contact with membrane interfaces. These include sensing membrane curvature and the level of lipid unsaturation [ 6 ], remodeling membranes into tubular or spherical intermediates [ 7 , 8 ], or acting as a shield to protect membranes or lipid droplets [ 9 , 10 ].

Ala, amphipathic, Val, Thramphipathic, and their polar residues uncharged vs. The amphipathic motif of intrinsically disordered stress protein CDeT from Craterostigma plantagineum is responsible for phosphatidic acid binding and protection of enzymes from damaging effects caused by desiccation. AH-containing fission-inducing proteins may require cofactors such as additional proteins e.

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Amphipathic adj. Amphipathic is a word used to describe a chemical compound containing both polar water-soluble and nonpolar not water-soluble portions in its structure. It may also relate to a chemical compound having both hydrophobic and hydrophilic regions. In biology, amphipathic molecules are important in the formation of biological membranes and micelles. Through them, the plasma membrane , in particular, is able to create an effective selective barrier so that not all substances can enter or exit the cell. Instead, some of them need transport mechanisms. This is essential in order to regulate their concentration inside the cell, and this, in turn, is crucial in maintaining homeostasis. Synonyms: amphiphilic. The term amphipathic is a descriptive word for a substance or a chemical compound that possesses both hydrophobic and hydrophilic portions in its structure.

Amphipathic

All living cells are surrounded by a cell membrane. Plant cells and animal cells contain a cell nucleus that is also surrounded by a membrane and holds the genetic information for the cell. Everything between the cell membrane and the nuclear membrane, including intracellular fluids and various subcellular components such as the mitochondria and ribosomes is called the cytoplasm. The lipids in cell membranes are amphipathic. They have dual characteristics: part of the lipid is ionic and therefore dissolves in water, whereas the rest has a hydrocarbon structure and therefore dissolves in nonpolar substances. The amphipathic lipids commonly found in membranes are phospholipids and glycolipids. Phospholipids are lipids containing phosphorus. The phosphate ion PO 4 3 - is one of the components used in their formation. It is a major component of cell membranes.

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Yu, S. In the crowding regime, an AH may act as a membrane anchor but is not required for destabilizing the bilayer; for example, Stachowiak et al. Fagarasanu A. Bacia, K. This is essential in order to regulate their concentration inside the cell, and this, in turn, is crucial in maintaining homeostasis. Figure S4. Autophagy 7, — The analysis of AHs is facilitated by bioinformatics tools such as Heliquest [ 11 ] which project any amino-acid sequence onto a helical wheel and calculate various parameters such as AH hydrophobicity, charge, and hydrophobic moment an index of the amphipathic character of the putative helix. ISBN The interaction of ARF1—GTP with model membranes is very strong, with a spontaneous dissociation rate in the order of minutes. Binding assays at the level of single liposomes represent a more sophisticated type of analysis [ 14 ]. Benzophenone photophores in biochemistry. Geometry of membrane fission.

The main difference between amphiphilic and amphipathic molecules is that amphiphilic molecules have less distinct hydrophilic and hydrophobic regions, whereas amphipathic molecules have distinct separations between hydrophilic and hydrophobic regions. Amphiphilic and amphipathic molecules are types of molecules that contain both hydrophobic and hydrophilic regions.

Chong S. Computational studies of plasma lipoprotein lipids. Cornell, R. Palomares-Jerez, M. Sathappa, M. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ekanayake, E. Post the Definition of amphipathic to Facebook Facebook. Moreover, we suppose that synuclein family of proteins can be also considered as a subfamily of AH-containing fission-inducing proteins. However, we should keep in mind that in the case of reverse topology fission, AHs insert into the proximal leaflet of the budding membrane-enclosed compartment, and not into the distal leaflet, as in the case of the normal-topology fission. Residues experiencing shifts one standard deviation above the average are I, T, R, and E A giant amphipathic helix from a perilipin that is adapted for coating lipid droplets. Differential requirement for ATG2A domains for localization to autophagic membranes and lipid droplets. Similarly, new fission proteins belonging to this subfamily might be discovered in the future, based on the identification of AHs in their structure.