| DNA-directed DNA polymerase | <enzyme> DNA-dependent DNA polymerases found in bacteria, animal and plant cells. During the replication process, these enzymes catalyze the addition of deoxyribonucleotide residues to the end of a DNA strand in the presence of DNA as template-primer. They also possess exonuclease activity and therefore function in DNA repair. Chemical name: Deoxynucleoside-triphosphate:DNA deoxynucleotidyltransferase (DNA-directed) Registry number: EC 2.7.7.7 (12 Dec 1998) |
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| COOH-terminal signal transamidase | <enzyme> Present in the endoplasmic reticulum; catalyses concomitant cleavage of the signal peptide of nascent proteins destined to be processed to a glycosylphosphatidylinositol (gpi) and addition of the gpi anchor Registry number: EC 2.3.2.- Synonym: cooh-ts-transamidase, gpi transamidase, gpti transamidase (26 Jun 1999) |
| signal | 1. Noticeable; distinguished from what is ordinary; eminent; remarkable; memorable; as, a signal exploit; a signal service; a signal act of benevolence. "As signal now in low, dejected state As erst in highest, behold him where he lies." (Milton) 2. Of or pertaining to signals, or the use of signals in conveying information; as, a signal flag or officer. The signal service, a bureau of the government (in the United States connected with the War Department) organised to collect from the whole country simultaneous raports of local meteorological conditions, upon comparison of which at the central office, predictions concerning the weather are telegraphed to various sections, where they are made known by signals publicly displayed. Signal station, the place where a signal is displayed; specifically, an observation office of the signal service. Synonym: Eminent, remarkable, memorable, extraordinary, notable, conspicuous. Origin: From signal, n., cf. F. Signale. Source: Websters Dictionary (01 Mar 1998) |
| signal detection (psychology) | A theory of psychophysics which characterises not only the acuity of an individual's discrimination but also the psychological factors that bias his judgment. (12 Dec 1998) |
| signal node | A firm supraclavicular lymph node, especially on the left side, sufficiently enlarged that it is palpable from the cutaneous surface; such a lymph node is so termed because it may be the first recognised presumptive evidence of a malignant neoplasm in one of the viscera. A signal node that is known to contain a metastasis from a malignant neoplasm is sometimes designated by an old eponym, Troisier's ganglion. Synonym: jugular gland, Virchow's node. (05 Mar 2000) |
| signal peptidase | A peptide present on proteins that are destined either to be secreted or to be membrane components. It is usually at the N terminus and normally absent from the mature protein. Normally refers to the sequence (ca 20 amino acids) that interacts with signal recognition particle and directs the ribosome to the endoplasmic reticulum where co translational insertion takes place. Could also refer to sequences that direct post translational uptake by organelles. Signal peptides are highly hydrophobic but with some positively charged residues. The signal sequence is normally removed from the growing peptide chain by signal peptidase, a specific protease located on the cisternal face of the endoplasmic reticulum. See: signal recognition particle. (18 Nov 1997) |
| signal peptidase complex | A peptide present on proteins that are destined either to be secreted or to be membrane components. It is usually at the N terminus and normally absent from the mature protein. Normally refers to the sequence (ca 20 amino acids) that interacts with signal recognition particle and directs the ribosome to the endoplasmic reticulum where co translational insertion takes place. Could also refer to sequences that direct post translational uptake by organelles. Signal peptides are highly hydrophobic but with some positively charged residues. The signal sequence is normally removed from the growing peptide chain by signal peptidase, a specific protease located on the cisternal face of the endoplasmic reticulum. See: signal recognition particle. (18 Nov 1997) |
| signal peptide | A peptide present on proteins that are destined either to be secreted or to be membrane components. It is usually at the N terminus and normally absent from the mature protein. Normally refers to the sequence (ca 20 amino acids) that interacts with signal recognition particle and directs the ribosome to the endoplasmic reticulum where co translational insertion takes place. Could also refer to sequences that direct post translational uptake by organelles. Signal peptides are highly hydrophobic but with some positively charged residues. The signal sequence is normally removed from the growing peptide chain by signal peptidase, a specific protease located on the cisternal face of the endoplasmic reticulum. See: signal recognition particle. (18 Nov 1997) |
| signal peptide p25-subunit IV cytochrome oxidase | <chemical> Similar in action to melittin Synonym: p25 presequence peptide-cytochrome oxidase, pre-ctox p25 (26 Jun 1999) |
| signal peptides | Additional polypeptide sequence of 25 to 30 residues at the amino-terminal or carboxy-terminal end of proteins. The signal sequence signals the cellular fate or destination of a newly synthesised protein directing it to its ultimate destination in the cell. These leaders are recognised by the signal recognition particle and bound by specific receptor sites on the outer surface of the endoplasmic reticulum. They are then transported into the cisterna of the endoplasmic reticulum and from there directed to their ultimate destination in the cell. In prokaryotes, the signal peptides attach to the plasma membrane. These signal sequences are ultimately removed by specific peptidases. (12 Dec 1998) |
| signal processing, computer-assisted | Computer-assisted processing of electric, ultrasonic, or electronic signals to interpret function and activity. (12 Dec 1998) |
| signal recognition particle | A complex between a 7S RNA and six proteins. SRP binds to the nascent polypeptide chain of eukaryotic proteins with a signal sequence and halts further translation until the ribosome becomes associated with the rough endoplasmic reticulum. One of the SRP proteins (srp54) binds GTP and in association with 7SRNA and srp19 has GTPase activity. (18 Nov 1997) |
| signal recognition particle receptor | Receptor for the signal recognition particle (SRP) found in the membrane of the endoplasmic reticulum. Also called docking protein. Heterodimeric, both protomers having GTP binding capacity, though dissimilar binding sites. Not until the complex of SRP, ribosome, message and nascent polypeptide chain binds to the SRP receptor is the block to further chain elongation released and concurrently the SRP is released, leaving the ribosome attached to the endoplasmic reticulum membrane. Cotranslational transport of the polypeptide delivers it into the lumen of the ER. (18 Nov 1997) |
| signal response coupling | The cascade of processes by which an extracellular signal (typically a hormone or neurotransmitter) interacts with a receptor at the cell surface, causing a change in the level of a second messenger for example calcium or cyclic AMP) and ultimately effects a change in the cells functioning (for example: triggering glucose uptake or initiating cell division). Can also be applied to sensory signal transduction, for example of light at photoreceptors. (18 Nov 1997) |
| signal sequence | A peptide present on proteins that are destined either to be secreted or to be membrane components. It is usually at the N terminus and normally absent from the mature protein. Normally refers to the sequence (ca 20 amino acids) that interacts with signal recognition particle and directs the ribosome to the endoplasmic reticulum where co translational insertion takes place. Could also refer to sequences that direct post translational uptake by organelles. Signal peptides are highly hydrophobic but with some positively charged residues. The signal sequence is normally removed from the growing peptide chain by signal peptidase, a specific protease located on the cisternal face of the endoplasmic reticulum. See: signal recognition particle. (18 Nov 1997) |