| retinoblastoma protein | <molecular biology, protein> Product of the retinoblastoma tumour suppressor gene. It is a nuclear phosphoprotein hypothesised to normally act as an inhibitor of cell proliferation. Rb protein is absent in retinoblastoma cell lines. It also has been shown to form complexes with the adenovirus e1a protein, the sv40 t antigen, and the human papilloma virus e7 protein. (03 Jul 1999) |
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| retinol-binding protein | <molecular biology> Proteins which bind with retinol. The retinol-binding protein found in plasma has an alpha-1 mobility on electrophoresis and a molecular weight of 21,000-22,000. The protein has one binding site for retinol and is responsible for the transport of vitamin A. The retinol- protein complex (molecular weight 80,000 to 90,000) circulates in plasma in the form of a protein-protein complex with prealbumin. The retinol-binding protein found in tissue has a molecular weight of 14,000 and carries retinol as a non-covalently-bound ligand. (03 Jul 1999) |
| PEP protein tyrosine phosphatase | <enzyme> Pest - pro, glu, ser and thr; an intracellular ptpase expressed primarily by cells of haematopoietic origin; involved in regulating nuclear tyrosine phosphorylation; amino acid sequence has been determined Registry number: EC 3.1.3.- Synonym: pep ptpase, pest-enriched phosphatase, ptp-pest (26 Jun 1999) |
| membrane protein | <protein> A protein with regions permanently attached to a membrane (peripheral membrane protein) or inserted into a membrane integral membrane protein). Insertion into a membrane implies hydrophobic domains in the protein. All transport proteins are integral membrane proteins. (18 Nov 1997) |
| channel protein | <chemistry, physiology> A protein that facilitates the diffusion of molecules/ions across lipid membranes by forming a hydrophilic pore. most frequently multimeric with the pore formed by subunit interactions. (18 Nov 1997) |
| G-protein | <cell biology, molecular biology> Intracellular membrane-associated proteins activated by several (e.g., beta adrenergic) receptors. They serve as second messengers or transducers of the receptor-initiated response to intracellular elements such as enzymes to initiate an effect. They are also mediators of activated cell-surface receptors and their enzymes or of ion channels. They are responsible for activating a chain of events that alters the concentration of intracellular signaling molecules such as cyclic AMP and calcium. In turn, these intracellular messengers alter the behaviour of other target proteins within the cell. These proteins have a high affinity for guanine nucleotides and hence are named "G" proteins. Synonym: G-protein, GTP-binding proteins. (12 Jul 2000) |
| G-protein coupled receptor | <cell biology> Cell surface receptors that are coupled to G-proteins (GTP-binding protein). G-protein coupled receptors are thought to have seven membrane spanning domains and have been divided into 2 subclasses: those in which the binding site is in the extracellular domain for example receptors for glycoprotein hormones, such as thyroid stimulating hormone (TSH) and follicle-stimulating hormone (FSH) and those in which the ligand binding site is likely to be in the plane of the 7 transmembrane domains for example rhodopsin and receptors for small neurotransmitters and hormones for example muscarinic acetylcholine receptor. (18 Nov 1997) |
| G-protein, inhibitory GI | A g-protein that inhibits adenylyl cyclase and activates k+ channels. (12 Dec 1998) |
| G-protein, stimulatory gs | A G-protein that mediates the receptor activation of adenylyl cyclase. (12 Dec 1998) |
| chemotactic protein methylesterase | <enzyme> Demethylates methyl-accepting chemotaxis proteins Registry number: EC 3.1.1.- Synonym: chemotactic methylesterase, carboxymethylesterase of chemotaxis, cheb methylesterase (26 Jun 1999) |
| peripheral membrane protein | <protein> Membrane proteins that are bound to the surface of the membrane and not integrated into the hydrophobic region. Usually soluble and were originally thought to bind to integral proteins by ionic and other weak forces (and could therefore be removed by high ionic strength, for example). However, it is now clear that some peripheral membrane proteins are covalently linked to molecules that are part of the membrane bilayer (see acylated proteins and glypiation) and that there are others that fit the original definition but are perhps more appropriately considered proteins of the cytoskeleton (e.g. Band 4.1 and spectrin) or extracellular matrix (e.g. Fibronectin). (18 Nov 1997) |
| peripheral protein | <protein> A water-soluble protein that is loosely bound (by hydrogen bonds orelectrostatic forces) to a membrane. (09 Oct 1997) |
| periplasmic protein disulfide oxidoreductase | <enzyme> Isolated from haemophilus influenzae; may be required for assembly or folding of one or more disulfide-containing cell envelope proteins; ccmg isolated from paracoccus denitrificans Registry number: EC 1.8.4.- Synonym: por disulfide oxidoreductase, por gene product, periplasmic oxidoreductase, ccmg gene product (26 Jun 1999) |
| ribose binding protein | <protein> Periplasmic binding proteins of bacteria that interact either with the ribose transport system or with the methyl accepting chemotaxis protein MCP III (trg). (18 Nov 1997) |
| ribosomal protein | <protein> Proteins present within the ribosomal subunits. In prokaryotes there are 31 proteins in the large subunit and 21 in the small subunit. Eukaryotic subunits have 50 (large subunit) and 33 (small subunit) proteins. (18 Nov 1997) |