gpcrs Flashcards
characteristics and features of signal transduction
contact dependent, secreted molecules
general features= specificity, sensitivity, amplification, modularity, desensitization & integration, localized response
G-protein coupled receptors
B-andregenic receptor, G protein, second messenger signaling, protein kinase, regulation and desensitization
general features of signal transduction
a signal (ligand) interacts with a receptor, activated receptor interacts with cellular machinery to produce a second signal or a change in protein activity, cellular metabolic activity changes, transduction event ends
two types of intercellular signal transduction
1)contact-dependent
2) secreted molecules
-> paracrine
-> endocrine
-> autocrine
-> synaptic
types of secreted signaling molecules
AAs, proteins, glycoproteins, small peptides, amines, lipids, nucleotides/nucleosides, gases
specificity
achieved by precise molecular complementarity between the signal and receptor molecules- mediated by weak (noncovalent) forces
amplification
results when an enzyme is activated by a signal receptor and in turn catalyzes the activation of many molecules of a second enzyme, & so on, in an enzyme cascade
modular
has multiple domains that recognize specific features- allows cells to mix and match a set of signaling molecules; phosphorylation provides reversible points of interaction
scaffold proteins
nonenzymatic proteins that bring together enzymes that interact in cascades
desensitized
no longer responsive to a signal- occurs when a signal is present continuously
integration
ability of the system to receive multiple signals & produce a unified response
response localization
cells confine signaling system components to a structure to regulate processes locally
first messenger
extracellular signal
second messenger
metabolite or ion
which statement describes the active form of the guanosine nucleotide-binding protein?
GTP binds the a subunit
G-protein coupled receptor
external ligand binding to receptor activates an intracellular GTP-binding protein, which regulates an enzyme that generates an intracellular second messenger
receptor enzyme (tyrosine kinase)
ligand binding activates tyrosine kinase activity by autophosphorylation; kinase activates transcription factor, altering gene expression (kinase cascade)
B-adrenergic receptor
epinephrine binds to specific receptor; hormone-recept or complex causes the GDP bound to Gsa to be replaced by GTP, activating Gsa; activated Gsa separates from GsB moves to adenylyl cyclase, and activates it. Many GsB subunits may be activated by one occupied receptor; adenylyl cyclase catalyzes the formation of cAMP; cAMP activates PKA; phosphorylation of cellular proteins by PKA causes the cellular response to epinephrine; cAMP is degraded, reversing the activation of PKA
