Term
| How does Nitric Oxide signaling work? |
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Definition
NO activates a soluble guanylate cyclase (an enzyme that converts GTP into
cyclic GMP (cGMP)); the elevated cGMP activates protein kinase G, which phosphorylates target proteins. One
notable result of NO signaling is vasodilation. |
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Term
| Phosphorylation of a protein can change what 3 things |
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Definition
(1) its interaction with other proteins (which can bring it into close proximity to new substrates, move it into the
nucleus, keep it out of the nucleus etc.),
(2) change its conformation so that it is now active or inactive or has a change in substrate specificity, or
(3) cause it to be degraded. |
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Term
The major mechanisms of signal termination are...
(4) |
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Definition
(1) dissociation
of signal (ligand) from receptor, (2) internalization and proteolysis of liganded receptors, (3) phosphatases and
phosphodiesterases, (4) feedback inhibition (this often occurs when an activated downstream kinase inactivates
upstream proteins by phosphorylation). |
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Term
| Give two examples of 7-transmembrane-helix receptors (7TM receptors, also called G-protein coupled receptors) |
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Definition
| Glucagon and epinephrine receptors |
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Term
| Most effects of cAMP in human cells are mediated by activation of a single kinase? What is that Kinase and how does cAMP activate it |
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Definition
| protein kinase A (PKA). This kinase is normally kept inactive by the binding of regulatory subunits. The binding of cAMP to the regulatory subunits leads to their dissociation and release of the free catalytic domains. |
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Term
| Name some of the substrates of protein kinase A and what they do. |
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Definition
Activated PKA has many substrates (signaling responses) including: phosphorylase kinase (increases glycogen breakdown), glycogen synthase (inactivating glycogen synthesis), phosphofructokinase-2/fructobisphosphatase-2 (reducing levels of F-2,6-BP which reduces flux through glycolysis in the liver), pyruvate kinase (again reducing flux through glycolysis in the liver), cAMP-response
element binding protein (CREB, which activates transcription of gluconeogenic enzymes and inhibits expression of glycolytic enzymes in the liver, among others). |
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Term
| Do all 7tm receptors activate cAMP through coupled g proteins? |
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Definition
No. Some of them deactivate cAMP. examples include: the alpha-adrenergic receptors, acetylcholine receptor and
many neurotransmitters. |
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Term
| Very small changes in IP3 concentration allow the highly cooperative opening of what kind of channels |
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Definition
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Term
| Some activated 7 TM receptors, including the glucagon receptor, also activate phospholipase C. What does phospholipase C do? |
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Definition
| hydrolyzes the phosphodiester bond connecting phosphorylated inositol to the acylated glycerol of phosphatidyl inositol 4,5-bisphosphate (PIP2). This cleavage of PIP2 produces two messengers: inositol 1,4,5-trisphosphate (IP3), a soluble molecule that can diffuse from the membrane, and diacylglycerol (DAG), which stays in the membrane. Both of which end up activating various isoforms of protein kinase C. DAG directly and IP3 indirectly by increasing calcium concentration |
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