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Membrane proteins exist in three topologies: polytopic, bitopic, and monotopic, depending on the distribution of their domains throughout the membrane. [15] The domains of polytopic proteins cross the membrane multiple times while bitopic proteins may only pass through the membrane once typically with a transmembrane helix connecting two ...
Membrane proteins fall into several broad categories depending on their location. 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 ...
The Protein Structure Initiative (PSI), funded by the U.S. National Institute of General Medical Sciences (NIGMS), part of the National Institutes of Health (NIH), has among its aim to determine three-dimensional protein structures and to develop techniques for use in structural biology, including for membrane proteins.
The alternative oxidase is an integral monotopic membrane protein that is tightly bound to the inner mitochondrial membrane from matrix side [18] The enzyme has been predicted to contain a coupled diiron center on the basis of a conserved sequence motif consisting of the proposed iron ligands, four glutamate and two histidine amino acid residues. [19]
Each subunit has three different structural domains: a short N-terminal epidermal growth factor domain; an α-helical membrane-binding moiety; and a C-terminal catalytic domain. PTGS (COX, which can be confused with " cytochrome oxidase ") enzymes are monotopic membrane proteins; the membrane-binding domain consists of a series of amphipathic ...
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.
Lanosterol synthase is a two-domain monomeric protein [10] composed of two connected (α/α) barrel domains and three smaller β-structures. The enzyme active site is in the center of the protein, closed off by a constricted channel. Passage of the (S)-2,3-epoxysqualene substrate through the channel requires a change in protein conformation.
carrier protein 1. A membrane protein that functions as a transporter, binding to a solute and facilitating its movement across the membrane by undergoing a series of conformational changes. [6] 2. A protein to which a specific ligand or hapten has been conjugated and which thereby carries an antigen capable of eliciting an antibody response ...