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The basic unit of the Reactome database is a reaction; reactions are then grouped into causal chains to form pathways [115] The Reactome data model allows us to represent many diverse processes in the human system, including the pathways of intermediary metabolism, regulatory pathways, and signal transduction, and high-level processes, such as ...
caffeine and theophylline inhibit cAMP phosphodiesterase, which degrades cAMP - thus enabling higher levels of cAMP than would otherwise be had. bucladesine (dibutyryl cAMP, db cAMP) - also a phosphodiesterase inhibitor; pertussis toxin, which increases cAMP levels by inhibiting Gi to its GDP (inactive) form. This leads to an increase in ...
Two-component systems accomplish signal transduction through the phosphorylation of a response regulator (RR) by a histidine kinase (HK). Histidine kinases are typically homodimeric transmembrane proteins containing a histidine phosphotransfer domain and an ATP binding domain, though there are reported examples of histidine kinases in the atypical HWE and HisKA2 families that are not ...
Up-regulation is a process which occurs within a cell triggered by a signal (originating internal or external to the cell), which results in increased expression of one or more genes and as a result the proteins encoded by those genes. Conversely, down-regulation is a process resulting in decreased gene and corresponding protein expression.
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events.Proteins responsible for detecting stimuli are generally termed receptors, although in some cases the term sensor is used. [1]
One measure of how well a molecule fits a receptor is its binding affinity, which is inversely related to the dissociation constant K d. A good fit corresponds with high affinity and low K d. The final biological response (e.g. second messenger cascade, muscle-contraction), is only achieved after a significant number of receptors are activated.
Bottom, signal enters the cell nucleus and causes transcription of DNA, which is then expressed as protein. The MAPK/ERK pathway (also known as the Ras-Raf-MEK-ERK pathway) is a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell.
The disequilibrium caused by these changes often causes withdrawal when the long-term use of a drug is discontinued. Upregulation and downregulation can also happen as a response to toxins or hormones. An example of upregulation in pregnancy is hormones that cause cells in the uterus to become more sensitive to oxytocin.