Receptors {cell-surface receptor} can use hundreds of genes.
peptides
Cell-surface receptors can bind acetylcholine, glutamate, glycine, and gamma-aminobutyric acid and endorphin and enkephalin peptides. Acetylcholine binds to sodium-ion-channel receptor. Glutamate binds to NMDA receptor. Glycine and GABA bind to chloride-ion-channel receptors. Receptor proteins using G proteins can couple to ion-channel proteins. Same-type receptors can have variable binding affinity and transport efficacy.
Alpha-adrenergic and beta-adrenergic cell-surface receptors {adrenergic receptor} can bind epinephrine and similar compounds.
membrane
Amino ends are outside membranes, and carboxyl ends are inside membranes. Seven helices pass through membrane.
functions
Adrenergic receptors can couple to G protein. Adrenergic receptors can activate or inhibit adenylate cyclase to make or decrease cAMP.
functions: phosphates
Adrenergic receptors can activate phospholipase to break down inositol phospholipids in membrane into inositol triphosphate and diacylglycerol. Inositol triphosphate makes calcium vesicles release calcium ions, which bind to calmodulin, which regulates enzymes such as protein kinase. Diacylglycerol activates protein-kinase C proteins. Phosphorylation causes conformational changes that expose active sites and activate protein kinases. Protein phosphatases, such as cytoplasmic CD45 membrane protein, remove phosphates.
Cell-surface receptor proteins {CD4 protein} can bind protein kinase at carboxyl ends inside membranes.
Cell-surface receptors {growth factor receptor} can bind growth factors. Growth factors activate 100 immediate early genes, which then make transcription factors.
structure
Growth-factor receptors pass one helix through membrane. Receptor is outside membrane. Kinase or cyclase is inside membrane.
types
Atrial naturietic peptide has protein kinase and guanylate cyclase. Activin receptor protein has serine-threonine kinase. Phosphoprotein phosphatase has tyrosine phosphatase. Growth factor receptor has tyrosine kinase.
Cell-surface receptors {hormone binding receptor} can bind hormones. Hormone-binding receptors affect G proteins inside cell membranes. G proteins use GTP to activate adenylate cyclase and make cAMP. cAMP affects protein kinase A, which then phosphorylates transcription factors, such as CRE-binding protein, that bind to cAMP response elements (CRE).
Muscle-synapse cell-surface receptors {nicotinic cholinergic receptor} can bind acetylcholine. Nicotinic receptors have membrane alpha-helix pores. Acetylcholine binds to two alpha helices. Four genes make protein receptors. Gene alleles have different mRNA splicings, making many slightly different nicotinic cholinergic receptors.
Cell-surface receptors {steroid receptor} can bind steroids. Steroids can cross membranes and bind to steroid-receptor proteins inside cells, allowing them to move to cell nucleus.
Cell-surface receptors can bind hormones and affect GTP-binding proteins {G protein} inside cell membranes. Activated G protein catalyzes its return to unactivated state, thus timing rate of G-protein processes. Immediate-early genes activated in learning use cAMP signal paths.
cyclic AMP
G protein uses GTP to activate adenylate cyclase and make cAMP. cAMP affects protein kinase A, which then phosphorylates CRE-binding protein, which binds to cAMP response elements (CRE).
senses
Olfactory sensors use G-protein transduction.
structure
G protein is similar to proteins for cross-membrane signaling, protein synthesis, cell molecule transport, and cross-membrane transport.
Steroid-receptor proteins bind to regulatory-region 15-base sequences {hormone-response element}, for activation or repression.
Chemicals {ionophore} can artificially raise cell calcium concentration.
Serine proteinases {plasminogen activator} can have cell-surface receptors. Urokinase plasminogen activator (uPA) can activate matrix metalloproteinases. Plasminogen-activator inhibitors counteract tissue plasminogen activator (tPA).
Retina rod-cell proteins {rhodopsin}| can absorb light and bind GTP to transducin, which activates phosphodiesterase, which breaks down cGMP, which closes cGMP-dependent ion channels and so causes hyperpolarization. Rhodopsin is similar to adrenergic receptor. Opsin proteins are similar to rhodopsin, because both use 11-cis-retinal as chromophore. Absorption maximum differs for opsins and rhodopsin.
GTP-binding proteins {transducin} can transduce signals in eye.
ATR protein, matrilins, integrins, and other cell-surface protein-interaction proteins have extra-cellular domains {von Willebrand factor type A}.
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Date Modified: 2022.0225