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An integral, or intrinsic, membrane protein (IMP) [1] is a type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins can be classified as IMPs, but not all IMPs are transmembrane proteins. [2] IMPs comprise a significant fraction of the proteins encoded in an organism's genome. [3]
In contrast, approximately 25% of all proteins are membrane proteins. [15] Their hydrophobic surfaces make structural and especially functional characterization difficult. [13] [16] Detergents can be used to render membrane proteins water-soluble, but these can also alter protein structure and function. [13]
Schematic representation of transmembrane proteins: 1) a single-pass membrane protein 2) a multipass membrane protein (α-helix) 3) a multipass membrane protein β-sheet. The membrane is represented in light yellow. A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane.
Intramembrane proteases are integral membrane proteins that are polytopic transmembrane proteins with multiple transmembrane helices. [5] [17] Their active sites are located within the transmembrane helices and form an aqueous environment within the hydrophobic lipid bilayer.
Integral proteins hold strong association with the lipid bilayer and cannot easily become detached. [9] They will dissociate only with chemical treatment that breaks the membrane. Peripheral proteins are unlike integral proteins in that they hold weak interactions with the surface of the bilayer and can easily become dissociated from the ...
Ion channels are integral membrane proteins, typically formed as assemblies of several individual proteins. Such "multi- subunit " assemblies usually involve a circular arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer .
Integral and lipid-anchored proteins are proposed to form three types of zones: proteins with an associated lipid fingerprint, [9] protein islands, and lipid-only voids. Although the latter do not contain proteins as part of their internal particle set or primary structure, they do contain proteins in their quaternary association with the ...
CD68 (also called gp110 or macrosialin) [5] is a heavily glycosylated integral membrane protein whose structure consists of a mucin-like domain followed by a proline-rich hinge; a single LAMP-like domain; a transmembrane region and a short cytoplasmic tail. CD molecules are leucocyte antigens on cell surfaces.