bis104 benjamin edward quiz and exams and notes_0002 - Page 3

Bis104 benjamin edward quiz and exams and notes_0002 - Page 3

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BIS 104 Cell Signaling (aka Signal Transduction) A. What is it? Information (from neighboring cells, environment) in the form of chemical stimuli is relayed across the plasma membrane to cell cytoplasm and nucleus. B. General features of signaling systems (figures 15.1, 2, 3). 1. Recognition of stimulus at outer surface of PM by specific receptor proteins. 2. Transfer of signal from outer surface of cell to inner leaflet of PM. 3. Transmission of signal to effector molecules on the inner leaflet and cytoplasm. 4. Cessation of response due to inactivation or degradation of signal molecules; accompanied by decrease in level of external stimulus. C. Alternative pathways. For some signaling molecules, no membrane receptors are required; they enter cell by passive diffusion. E.g., steroids, nitric oxide; acetylcholine, retinoic acid. D. Basic characteristics of cell signaling systems: 1. Series of protein conformational changes, usually mediated by
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Unformatted text preview: protein kinases and phosphatases. a. Human genome codes for > 500 kinases; >100 phosphatases. b. Approx. 50% of all proteins in a cell are potential substrates for phosphorylation. 2. GTP-binding proteins (G-proteins) function as on / off switches. a. Nucleotide binding causes conformational change in G-protein (GTP = on; GDP = off). b. G-proteins have weak intrinsic GTPase activity; this can be stimulated by interaction with GTPase Activating Proteins (GAPs). c. G-protein regulators i. GAPs (GTPase activating proteins) shorten duration of "on" response by speeding up GTPase activity. ii. GEFs (guanine nucleotide exchange proteins): enhance release of GDP; facilitates binding of available GTP = "on". iii. GNDIs (guanine nucleotide dissociation inhibitors): inhibit release of bond GDP, thus enhancing the "off signal. Demo...
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This note was uploaded on 05/24/2010 for the course BIS 104 taught by Professor Scholey during the Spring '08 term at UC Davis.

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