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The regulatory protein subunits of many ion channels and transmembrane receptors, for example, may be defined as peripheral membrane proteins. In contrast to integral membrane proteins, peripheral membrane proteins tend to collect in the water-soluble component, or fraction, of all the proteins extracted during a protein purification procedure.
Peripheral membrane proteins are temporarily attached either to the lipid bilayer or to integral proteins by a combination of hydrophobic, electrostatic, and other non-covalent interactions. Peripheral proteins dissociate following treatment with a polar reagent, such as a solution with an elevated pH or high salt concentrations. [citation needed]
The integrin VLA-4 is expressed on the cell surfaces of stem cells, progenitor cells, T and B cells, monocytes, natural killer cells, eosinophils, but not neutrophils. It functions to promote an inflammatory response by the immune system by assisting in the movement of leukocytes to tissue that requires inflammation. [ 2 ]
Aquaporin 2 is regulated by vasopressin which, when bound to the cell-surface receptor, activates the cAMP signaling pathway. This results in aquaporin-2 containing vesicles to increase water uptake and return to circulation. Mutation of the aquaporin 2 vasopressin receptor is a cause of acquired diabetes insipidus.
Cell adhesion molecules (CAMs) are a subset of cell surface proteins [1] that are involved in the binding of cells with other cells or with the extracellular matrix (ECM), in a process called cell adhesion. [2] In essence, CAMs help cells stick to each other and to their surroundings.
Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another.
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 .
An APC takes up an antigenic protein, performs antigen processing, and returns a molecular fraction of it—a fraction termed the epitope—and displays it on the APC's surface coupled within an MHC class II molecule (antigen presentation). On the cell's surface, the epitope can be recognized by immunologic structures like T-cell receptors (TCRs