| elongation factor | <biochemistry> Peptidyltransferase components of ribosomes that catalyse formation of the acyl bond between the incoming amino acid residue and the peptide chain. There are three classes of elongation factor: EF1_ (EF Tu in prokaryotes) binds GTP and aminoacyl tRNA, delivering it to the A site of ribosomes. EF 1_ (EF Ts) helps in regeneration of GTP EF 1_. EF 2 (EF G) binds GTP and peptidyl tRNA and translocates it from the A site to the P site. Diptheria toxin inhibits protein synthesis in eukaryotes by adding an ADP ribosyl group to a modified histidine residue (dipthamide) in elongation factor II. (18 Nov 1997) |
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| peptide elongation factor tu | A protein found in bacteria and eukaryotic cells which delivers aminoacyl-trna's to the a site of the ribosome. The aminoacyl-trna is first bound to a complex of elongation factor tu containing a molecule of bound GTP. The resulting complex is then bound to the 70s initiation complex. Simultaneously the GTP is hydrolyzed and a tu-GDP complex is released from the 70s ribosome. The tu-GTP complex is regenerated from the tu-GDP complex by the ts elongation factor and GTP. (12 Dec 1998) |
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| peptide chain elongation | The process whereby an amino acid is joined through a substituted amide linkage to a chain of peptides. (12 Dec 1998) |
| peptide elongation factors | Protein factors uniquely required during the elongation phase of protein synthesis. (12 Dec 1998) |
| sign of elongation | <microscopy> Referring to the elongation of a substance in relation to refractive indices. If it is elongated in the direction of the high refractive index, it is said to have a positive sign of elongation. If it is elongated in the direction of the low refractive index, it has a negative sign of elongation, not to be confused with the sign of double refraction (i.e., optic sign). (05 Aug 1998) |
| elongation | <radiobiology> Parameter indicating the degree to which the cross-section of a toroidal plasma is non-circular. Kappa=b/a, where b and a are the vertical and horizontal minor radii. As kappa is increased, the confinement in relation to the total current improves, but the plasma also becomes more and more unstable to vertical displacements. A circular plasma has kappa of 1, a common value for elongated plasmas is 1.7, and the absolute limit is probably around 2. (09 Oct 1997) |
| accelerator factor | <chemical> Heat- and storage-labile plasma glycoprotein which accelerates the conversion of prothrombin to thrombin in blood coagulation. Factor v accomplishes this by forming a complex with factor xa, phospholipid, and calcium (prothrombinase complex). Deficiency of factor v leads to owren's disease. Chemical name: Blood-coagulation factor V (12 Dec 1998) |
| acetate replacement factor | <biochemistry> 1,2 dithiolane 3 valeric acid. Regarded as a coenzyme in the oxoglutarate dehydrogenase complex of the citric acid cycle. Involved generally in oxidative decarboxylations of _ keto acids. A growth factor for some organisms. (18 Nov 1997) |
| adrenal weight factor | A postulated substance of adenohypophysial origin responsible for maintenance of the weight of the adrenal cortex. (05 Mar 2000) |
| adrenocorticotropic releasing factor | Hormone produced by hypothalamus that causes pituitary to secrete adrenocorticotropic hormone. (05 Mar 2000) |
| a-factor | <molecular biology> A protein which is found in the bacterial genus Streptomyces that helps start the production of streptomycin and the process of morphological differentiation. It is used in biotechnology to induce these functions in mutant strains of Streptomyces that cannot produce it themselves. (09 Feb 1998) |
| angiogenesis factor | Substance causing proliferation of new blood vessels. It is found in tissues with high metabolic requirements, such as the retina, and in certain cancers. The factor is also released by hypoxic macrophages at the edges or outer surfaces of wounds and initiates revascularization in wound healing. (12 Dec 1998) |
| animal protein factor | <biochemistry> Member of the water soluble B vitamin group, important in the proper function of the nervous system and important in proper carbohydrate, protein and fat metabolism. (27 Sep 1997) |
| antialopecia factor | A member of the vitamin B complex necessary for growth of yeast and of mice, absence from the diet causes hair loss and dermatitis in mice. (27 Sep 1997) |
| antianaemic factor | <biochemistry> Member of the water soluble B vitamin group, important in the proper function of the nervous system and important in proper carbohydrate, protein and fat metabolism. (27 Sep 1997) |
| antiberiberi factor | Synonym: thiamin. (05 Mar 2000) |