1. audible or visible indications to animals in behavioral conditioning. Many signals have had long-term use in the animal world and are used worldwide. Whoa and Getup, Heel and Sit are common examples. Getawayback is perhaps more colloquial. Many sheepdogs are trained to react to whistles and performing animals are usually trained to react to gestures with the hand.
2. in biochemical terminology relates to staging in reactions; see signal sequence.
- s. peptidase — an integral membrane protein located on the luminal surface of the endoplasmic reticulum that cleaves the signal peptide and frees the protein for folding and export.
- s. recognition particle (SRP) — a particle composed of six different proteins and one small (7S) RNA that binds to the signal peptide as it emerges from the ribosome, temporarily halting the synthesis of the protein while the complex is transported to the endoplasmic reticulum where the SRP recognizes and docks to a docking protein located on the cytoplasmic surface followed by the transfer of the ribosome to a ribosome receptor on the membrane; the SRP and its docking protein are released from the ribosome and translation resumes.
- s. transduction proteins — proteins which may be a protein kinase, an ion channel forming protein (as in nerve cells), or a protein that undergoes some energy dependent change in which the energy is supplied by the hydrolysis of a higher energy compound such as guanosine triphosphate.
