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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 ]
Depending on the number of transmembrane segments, transmembrane proteins can be classified as single-pass membrane proteins, or as multipass membrane proteins. [2] Some other integral membrane proteins are called monotopic, meaning that they are also permanently attached to the membrane, but do not pass through it. [3]
Integral polytopic proteins are transmembrane proteins that span across the membrane more than once. These proteins may have different transmembrane topology. [4] [5] These proteins have one of two structural architectures: Helix bundle proteins, which are present in all types of biological membranes;
Protein channel proteins, also called permeases, are usually quite specific, and they only recognize and transport a limited variety of chemical substances, often limited to a single substance. Another example of a transmembrane protein is a cell-surface receptor, which allow cell signaling molecules to communicate between cells.
Comparison of transport proteins A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across the cell membrane at the same time, and is, therefore, a type of ...
Schematic diagram of the 2D structure of aquaporin 1 depicting the six transmembrane alpha-helices and the five interhelical loop regions A-E The 3D structure of aquaporin Z highlighting the 'hourglass'-shaped water channel that cuts through the center of the protein. Aquaporin proteins are composed of a bundle of six transmembrane α-helices ...
Also known as ionotropic receptors, this group of channels open in response to specific ligand molecules binding to the extracellular domain of the receptor protein. [15] Ligand binding causes a conformational change in the structure of the channel protein that ultimately leads to the opening of the channel gate and subsequent ion flux across ...
Facilitated diffusion in cell membrane, showing ion channels and carrier proteins. Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins. [1]