Term
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Definition
| achieved by precise molecular complementarity between the signal & receptor molecules & mediated by the same kinds of weak forces that mediate enzyme-substrate & antigen-antibody interactions |
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Definition
| the dissociation constant between signal & receptor which is commonly 10^-10 M or less which means that the receptor detects picomolar concentrations of a signal molecule |
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Definition
| a factor in receptor-ligand interactions which results in large changes in receptor activation with small changes in ligand concentration |
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Definition
| results when an enzyme associated with a signal receptor is activated & in turn catalyzes the activation of many molecules of a third enzyme & so on in an "enzyme cascade" |
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Definition
| a factor of interacting signaling proteins which allows a cell to mix & match a set of signaling molecules to create complexes with different functions or cellular locations |
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Definition
| nonenzymatic proteins; have an affinity for several enzymes that interact in cascades to bring those proteins together to ensure their interaction as specific cellular locations & at specific times |
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Definition
| occurs when a signal is present continuously; affects the receptor system; when the stimulus falls below a certain threshold, the system again becomes sensitive |
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Term
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Definition
| a feature of signal-transducing systems; the ability of the system to receive multiple signals & produce a unified response appropriate to the needs of the cell or organism |
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Term
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Definition
1. G protein-coupled receptors
2. receptor tyrosine kinases
3. receptor guanylyl cyclases
4. gated ion channels
5. adhesion receptors
6. nuclear receptors |
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Term
| What is the relationship between G protein-coupled receptors (GPCRs) & guanosine nucleotide-binding protein (G protein)? |
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Definition
| GPCRs are receptors that are closely associated with a member of the G protein family |
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Term
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Definition
| generated by an activated enzyme; affects downstream targets |
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Term
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Definition
| one of 4 general types (alpha 1, alpha 2, beta 1, & beta 2) that are defined by differences in their affinities & responses to a group of agonists & antagonists |
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Term
| What is the relationship between agonists & antagonists? |
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Definition
| agonists are structural analogs that bind to a receptor & mimic the effects of its natural ligand; antagonists are analogs that bind the receptor without triggering the normal effect & thereby block the effects of agonists including the biological ligand |
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Term
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Definition
| the alternative name for GPCRs because they all are integral proteins with seven hydrophobic, helical regions of 20 to 28 amino acid residues that span the plasma membrane seven times |
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Term
| stimulatory G protein (Gs) |
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Definition
| a G protein that activates its effector |
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Term
| cAMP-dependent protein kinase (protein kinase A) (PKA) |
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Definition
| allosterically activated by cyclic AMP |
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Term
| cyclic nucleotide phosphodiesterase |
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Definition
| hydrolyzes cAMP to 5'-AMP |
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Term
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Definition
| a protein that gets a binding site when receptors are phosphorylated; its binding effectively prevents further interaction between the receptor & the G protein |
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Term
| G protein-coupled receptor kinases (GRKs) |
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Definition
| a protein family which includes proteins like beta-adrenergic receptor kinase; all of this family phosphorylates GPCRs on their carboxyl-terminal cytoplasmic domains & play roles in desensitization & resensitization of their receptors |
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Term
| cAMP response element binding protein (CREB) |
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Definition
| phosphorylated by the catalytic subunit of PKA when that subunit moves into the nucleus; alters the expression of specific genes regulated by cAMP |
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Term
| inhibitory G protein (Gi) |
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Definition
| activated by the binding of somatostatin to its receptor; a structurally homologous protein to Gs which inhibits adenylyl cyclase & lowers [cAMP] |
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Term
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Definition
| confine the signaling process to a specific region of the cell to allow for so many types of signals to be mediated by a single second messenger; noncatalytic proteins that hold together other protein molecules that function in concert |
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Term
| AKAPs (A kinase anchoring proteins) |
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Definition
| multivalent adaptor proteins (one part binds to the R subunits of PKA & another to a specific structure in the cell, confining the PKA to the vicinity of that structure) |
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Term
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Definition
| a class of GPCRs that are coupled through a G protein to a plasma membrane; specific for the membrane phospholipids phosphatidylinositol 4,5-bisphosphate (PIP2) |
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Term
| 2 potent second messengers whose production is catalyzed by the activation of PIP2-specific PLC (activated by an activated Gq) |
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Definition
1. diacylglycerol
2. inositol 1,4,5-triphosphate (IP3) |
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Term
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Definition
| activated by elevated [Ca2+] |
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Term
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Definition
| an acidic protein with four high-affinity Ca2+-binding sites |
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Term
| receptor tyrosine kinases (RTKs) |
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Definition
| a large family of plasma membrane receptors with intrinsic protein kinase activity that transduce extracellular signals by a mechanism fundamentally different from that of GPCRs |
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Term
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Definition
| where a P-Tyr residue of IRS-1 binds; part of the protein Grb2 |
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Term
| What is the relationship between "ras" & "small G proteins" |
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Definition
| Ras is the prototype of a family of small G proteins that mediate a wide variety of signal transductions |
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Term
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Definition
| mediate signaling initiated by a variety of growth factors (ex. platelet-derived growth factor & epidermal growth factor) |
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Term
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Definition
| the developmental signal; ex) erythropoietin (a 165 amino acid protein produced in the kidneys) |
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Term
| guanosine 3',5'-cyclic monophosphate (cyclic GMP, cGMP) |
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Definition
| a second messenger that is created when activated receptor enzymes called guanylyl cyclases convert GTP into this |
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Term
| cGMP-dependent protein kinase (protein kinase G) (PKG) |
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Definition
| mediates many of the actions of cGMP in animals |
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Term
| atrial natriuretic factor (ANF) |
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Definition
| the peptide hormone which activates guanylyl cyclase in the kidney |
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Term
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Definition
| a peptide which activates the receptor guanylyl cyclase in the plasma membrane of the epithelial cells of the intestine |
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Term
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Definition
| a Ca2+ dependent enzyme that produces nitric oxide from arginine |
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Term
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Definition
| relieved by NO-induced relaxation of cardiac muscle (same response brought about by nitroglycerin & other nitrovasodilators); the pain caused by contraction of a heart deprived of O2 because of blocked coronary arteries |
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Term
| voltage-gated Na+ channels |
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Definition
| exist along the entire length of the axon; closed when the membrane is at rest but open briefly when the membrane is depolarized locally in response to acetylcholine |
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Term
| voltage-gated K+ channels |
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Definition
| distributed along the axon; open a split second after voltage-gated Na+ channels in response to the depolarization when nearby Na+ channels open |
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Term
| voltage-gated Ca2+ channels |
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Definition
| at the distal end of the axon; open when the wave of depolarization & repolarization (caused by the activity of Na+ & K+ channels) arrives to trigger the release of the neurotransmitter acetylcholine (which carries the signal to another neuron or to a muscle fiber |
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Term
| nicotinic acetylcholine receptor |
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Definition
| mediates the passage of the signal from an electrically excited neuron at some types of synapses & at neuromuscular junctions to trigger muscle contraction |
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Term
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Definition
| receptors that are themselves ion channels; different from receptors that generate second messengers |
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Term
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Definition
| an integral protein with seven membrane-spanning alpha helices (the characteristic GPCR architecture) |
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Term
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Definition
| covalently attached to the light-absorbing pigment 11-cis-retinal; the protein component of rhodopsin whose covalent attachment occurs through a Schiff base to a Lys residue |
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Term
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Definition
| a protein that interacts with rhodopsin when rhodopsin is in its excited conformation; exists close to rhodopsin on the cytoplasmic face of the disk membrane |
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Term
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Definition
| a Ca2+-binding protein; inhibits rhodopsin (but this inhibition is relieved when [Ca2+] drops after illumination |
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Term
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Definition
| a protein which binds the phosphorylated carboxyl-terminal domain of rhodopsin; prevents further interaction between activated rhodopsin & transducin |
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Term
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Definition
| a small depolarization produces when there is an influx of Na+ & Ca2+ due to opening of the cAMP-gated Na+ & Ca2+ channels of the ciliary membrane |
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Term
| What is the relationship between cyclin & cyclin-dependent protein kinase (CDK)? |
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Definition
| Some kinases are heterodimers with a regulatory subunit (cyclin) & a catalytic subunit (cyclin-dependent protein kinase) |
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Term
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Definition
| a protein brought together with the cyclin by the protein DBRP to initiate the process of cyclin degradation |
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Term
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Definition
| a proteolytic enzyme complex whose signal comes from ubiquitin molecules being appended; degrades cyclin |
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Term
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Definition
| an extracellular signal that regulates synthesis of E2F; works with cytokines in such a way that they are essential compounds for the division of mammalian cells in nature |
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Term
| retinoblastoma protein (pRb) |
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Definition
| a very important CDK substrate; participates in a mechanism that arrests cell division in G1 when DNA damage is detected |
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Term
| What is the relationship between oncogenes & proto-oncogenes? |
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Definition
| oncogenes were originally discovered in tumor-causing viruses, then later found to be derived from genes in the animal host cells (proto-oncogenes) which encode growth-regulating proteins |
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Term
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Definition
| encode proteins that normally restrain cell division |
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Term
| programmed cell death (apoptosis) |
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Definition
| the process through which many cells can precisely control the time of their own death |
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Term
| hormone response elements (HREs) |
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Definition
| specific regulatory sequences in DNA with which a receptor protein can interact when hormone binding triggers changes in the receptor's conformation |
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Term
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Definition
| a drug that demonstrate the specificity of the steroid-receptor interaction; used to treat breast cancer |
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Term
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Definition
| a drug that acts as a steroid analog; binds to the progesterone receptor & blocks hormone actions essential to implantation of the fertilized ovum in the uterus to act as a contraceptive |
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