G protein (redirected from Stimulatory gs G-protein)

protein /pro·tein/ (pro´tēn) any of a group of complex organic compounds containing carbon, hydrogen, oxygen, nitrogen, and sulfur. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist of α-amino acids joined by peptide linkages. Twenty different amino acids are commonly found in proteins, each protein having a unique, genetically defined amino acid sequence that determines its specific shape and function. Their roles include enzymatic catalysis, transport and storage, coordinated motion, nerve impulse generation and transmission, control of growth and differentiation, immunity, and mechanical suppport.

---

AA protein  see under amyloid.

acute phase protein  any of the non-antibody proteins found in increased amounts in serum during the acute phase response, including C-reactive protein and fibrinogen.

AL protein  see under amyloid.

amyloid A protein  AA amyloid.

amyloid light chain protein  AL amyloid.

amyloid precursor protein  (APP) a large transmembrane glycoprotein expressed on the cell surface and of uncertain function; endocytosis and cleavage can produce abnormal 40 to 43 amino acid peptides which aggregate to form A, associated with Alzheimer's disease.

Bence Jones protein  a low-molecular-weight, heat-sensitive urinary protein found in multiple myeloma, which coagulates when heated to 45°–55°C and redissolves partially or wholly on boiling.

binding protein 

1. any protein able to specifically and reversibly bind other substances, such as ions, sugars, nucleic acids, or amino acids; they are believed to function in transport.

2. transport p.

protein C  a vitamin K–dependent plasma protein that, when activated by thrombin, inhibits the clotting cascade by enzymatic cleavage of factors V and VIII and also enhances fibrinolysis. Deficiency results in recurrent venous thrombosis.

C4 binding protein  a complement system regulatory protein that inhibits activation of the classical pathway.

complete protein  one containing the essential amino acids in the proportion required in the human diet.

compound protein , conjugated protein any of those in which the protein is combined with nonprotein molecules or prosthetic groups other than as a salt; e.g., nucleoproteins, glycoproteins, lipoproteins, and metalloproteins.

C-reactive protein  a globulin that forms a precipitate with the C-polysaccharide of the pneumonococcus; the most predominant of the acute phase proteins.

cystic fibrosis transmembrane regulator protein  a transmembrane protein produced by the cystic fibrosis gene, primarily functioning as a chloride channel. Numerous mutated forms of the gene have been associated with clinical cystic fibrosis.

fibrillar protein  any of the generally insoluble proteins that comprise the principal structural proteins of the body, e.g., collagens, elastins, keratin, actin, and myosin.

G protein  any of a family of proteins of the intracellular portion of the plasma membrane that bind activated receptor complexes and, through conformational changes and cyclic binding and hydrolysis of GTP, effect alterations in channel gating and so couple cell surface receptors to intracellular responses.

glial fibrillary acidic protein  (GFAP) the protein forming the glial filaments of the astrocytes and used as an immunohistochemical marker of these cells.

globular protein  any of the water-soluble proteins yielding only α-amino acids on hydrolysis, including most of the proteins of the body, e.g., albumins and globulins.

guanyl-nucleotide-binding protein  G p.

heat shock protein  any of a group of proteins first identified as synthesized in response to hyperthermia, hypoxia, or other stresses and believed to enable cells to recover from these stresses. Many have been found to be molecular chaperones and are synthesized abundantly regardless of stress.

HIV proteins  proteins specific to the human immunodeficiency virus; presence of certain specific HIV proteins together with certain HIV glycoproteins constitutes a serological diagnosis of HIV infection.

incomplete protein  one having a ratio of essential amino acids different from that of the average body protein.

membrane cofactor protein  (MCP) an inhibitor of complement activation found in most blood cells, endothelial and epithelial cells, and fibroblasts.

myeloma protein  any of the abnormal immunoglobulins or fragments, such as Bence-Jones proteins, secreted by myeloma cells.

partial protein  incomplete p.

plasma proteins  all the proteins present in the blood plasma, including the immunoglobulins.

prion protein  (PrP) a protein of uncertain function, in humans coded for by a gene on the short arm of chromosome 20. The protease-resistant core is the functional, and perhaps only, component of prions; several abnormal forms have been identified and are responsible for prion disease.

protein S  a vitamin K–dependent plasma protein that inhibits blood clotting by serving as a cofactor for activated protein C.

S protein  see vitronectin.

SAA protein  serum amyloid A p.

serum proteins  proteins in the blood serum, including immunoglobulins, albumin, complement, coagulation factors, and enzymes.

serum amyloid A protein  SAA p.; a high-molecular-weight protein synthesized in the liver; it is an acute phase protein and circulates in association with HDL lipoprotein. It is the precursor to AA amyloid and accumulates in inflammation.

sphingolipid activator protein  (SAP) any of a group of non-enzymatic lysosomal proteins that stimulate the actions of specific lysosomal hydrolases by binding and solubilizing their sphingolipid substrates.

transport protein  a protein that binds to a substance and provides a transport system for it, either in the plasma or across a plasma membrane.

---

G protein

a regulatory protein which becomes activated when bound to GTP and is involved in signal transduction.

---

G protein coupled receptor

a member of a large class of cell-surface signaling receptors that contain seven transmembrane a helices; ligand binding results in activation of a coupled trimeric G protein that then initiates intracellular signal transduction pathways.