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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]
Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane (integral monotopic). Peripheral membrane proteins are transiently associated with the cell membrane.
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.
It is found in the intestinal mucosa, especially in the columnar epithelium and goblet cells of the apical surface of the membrane, where it carries out the function of chloride and bicarbonate exchange. [39] Protein DRA's reuptake of chloride is critical to creating an osmotic gradient that allows the intestine to reabsorb water. [40]
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
The exception is the beta-4 subunit, which has a cytoplasmic domain of 1,088 amino acids, one of the largest of any membrane protein. Outside the cell membrane, the α and β chains lie close together along a length of about 23 nm; the final 5 nm N-termini of each chain forms a ligand-binding region for the ECM.
Phospholipid bilayers contain different proteins. These membrane proteins have various functions and characteristics and catalyze different chemical reactions. Integral proteins span the membranes with different domains on either side. [6] Integral proteins hold strong association with the lipid bilayer and cannot easily become detached. [9]
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.