Chapter 14. Signal-Transduction Pathways Flashcards
a ubiquitous protein in vertebrates that, when bound to calcium, stimulates many enzymes and transporters.
Calmodulin (CaM)
a type of regulatory protein that is activated by binding GTP and inactivated by the conversion of GTP to GDP.
G protein
a helix-loop-helix motif that forms a binding site for calcium; found in many calcium-sensitive proteins.
EF hand
a small molecule that binds to a protein, inducing a specific structural change. For instance, a steroid is a ligand for a steroid-hormone receptor.
Ligand
Interactions between several signaling pathways. Cross talk permits more finely tuned regulation of cell activity than would the action of individual independent pathways.
Cross talk
a class of integral membrane proteins typified by transducin in which the intramembrane portion consists of seven helical regions; these receptors are always coupled to G proteins.
G-protein-coupled receptor (GPCR)
A polypeptide hormone secreted by the á cells of the pancreas, that stimulates fuel storage and protein synthesis.
Insulin
a protein kinase that is activated by the binding of a Ca<2+> -calmodulin complex.
Calmodulin-dependent protein kinase (CaM kinase)
The enzyme that catalyzes the cleavage of phosphatidylinositol 4,5-bisphosphate into the two second messengers, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG), thereby activating the phosphoinositide cascade
Phospholipase C
a signal transduction pathway that employs cAMP and a series of enzymes to convert an extracellular signal into an intracellular signal.
Adenylate cyclase
A phospholipid present in cell membranes. Cleavage of phosphatidylinositol 4,5-bisphosphate releases intracellular signals that activate the phosphoinositide cascade.
Phosphatidylinositol 4,5-biphosphate (PIP2)
A receptor tyrosine kinase that mediates the action of insulin.
Insulin receptor
A set of reactions that convert an extracellular signal into an intracellular one; the conversion entails the cleavage of the phospholipid phosphatidyl inositol 4,5-bisphosphate into two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol.
Phosphoinositide cascade
Adaptor proteins that bind to phosphorylated insulin receptor and, in turn, are phosphorylated by the receptor. Other proteins bind to the phosphorylated IRS to propagate the insulin signal.
Insulin-receptor substate (IRS)
Proteins that interact with small G proteins that facilitate the exchange of GTP for GDP.
Guanine-nucleotide-exchange factor (GEF)
A receptor tyrosine kinase that is activated by epidermal growth factor. The unbound receptor exists as a monomer, but dimerizes upon growth factor binding.
EGF receptor (EGFR)
Non-enzymatic proteins that serve to tether the downstream components of a signaling pathway to the membrane.
Adaptor protein
A molecular structure on the EGF receptor that is exposed only upon binding EGF and that subsequently reaches out and inserts into a binding pocket on another EGF receptor monomer, facilitating dimerization.
Dimerization arm
Proteins that interact with GTP-bound small G proteins and facilitate GTP hydrolysis.
GTPase-activating protein (GAP)
Intracellular kinases, which are activated by reception of signals from outside the cell, that are members of signal transduction cascades.
Extracellular signal-regulated kinase (ERK)
a gene whose expression contributes to the development of cancer.
Oncogene
A 6-kd polypeptide that stimulates the growth of epidermal and epithelial cells.
Epidermal growth factor (EGF)
This domain binds phosphoinositide and acts with a phosphotyrosine-binding domain to anchor the IRS protein to the insulin receptor and the associated membrane.
pleckstrin homology domain
A protein kinase that is activated by the binding of diacylglycerol.
Protein kinase C (PKC)
small signal molecules whose concentration is changed in response to a primary messenger
Second messenger
a protein kinase that consists of two catalytic subunits and two regulatory subunits, which inhibit the catalytic subunits. Upon binding of cAMP, the regulatory subunits dissociate from the catalytic subunits, which then become active.
Protein kinase A (PKA)
A 7 transmembrane helix receptor for epinephrine (adrenaline).
β-adrenergic receptor (β-AR)
The photoreceptor of rod cells. It is composed of the protein opsin and the prosthetic group 11-cis-retinal.
Rhodopsin
a class of integral membrane proteins typified by transducin in which the intramembrane portion consists of seven helical regions; these receptors are always coupled to G proteins.
Seven-transmembrane-helix (7TM) receptor
the information embodied in the interaction of ligand with its receptor molecule.
Primary messenger
A kinase that catalyzes the transfer of a phosphoryl group from ATP to the hydroxyl group of tyrosine.
Tyrosine kinase
A kinase that phosphorylates and inactivates the β-adrenergic receptor.
β-adrenergic receptor kinase
transmembrane receptor proteins that, when bound to the appropriate signal molecules, display intracellular protein kinase activity, phosphorylating proteins on a tyrosine residue.
Receptor tyrosine kinase
domains of approximately 100 amino acids that bind to phosphotyrosine residues.
Src homology 2 (SH2) domain
a monomeric guanyl nucleotide binding protein that is active when bound to GTP and inactive when bound to GDP. These proteins have inherent GTPase activity.
Small G protein
Genes for DNA-repair proteins that suppress tumor development when at least one copy of the gene is free of a deleterious mutation.
Tumor-suppressor gene
signal transduction proteins that usually regulate cell growth in some fashion. When mutated, these genes become oncogenes and contribute to the development of cancer.
Proto-oncogene
domains that bind proline-rich stretches of polypeptide.
Src homology 3 (SH3) domain
A member of a class of signal transduction proteins called small G proteins. These proteins bind GDP in their inactive forms and GTP in their active forms.
Ras
