Chapter 14. Signal-Transduction Pathways

Question 1

a ubiquitous protein in vertebrates that, when bound to calcium, stimulates many enzymes and transporters.

Answer 1

Calmodulin (CaM)

Question 2

a type of regulatory protein that is activated by binding GTP and inactivated by the conversion of GTP to GDP.

Answer 2

G protein

Question 3

a helix-loop-helix motif that forms a binding site for calcium; found in many calcium-sensitive proteins.

Answer 3

EF hand

Question 4

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.

Answer 4

Ligand

Question 5

Interactions between several signaling pathways. Cross talk permits more finely tuned regulation of cell activity than would the action of individual independent pathways.

Answer 5

Cross talk

Question 6

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.

Answer 6

G-protein-coupled receptor (GPCR)

Question 7

A polypeptide hormone secreted by the á cells of the pancreas, that stimulates fuel storage and protein synthesis.

Answer 7

Insulin

Question 8

a protein kinase that is activated by the binding of a Ca<2+> -calmodulin complex.

Answer 8

Calmodulin-dependent protein kinase (CaM kinase)

Question 9

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

Answer 9

Phospholipase C

Question 10

a signal transduction pathway that employs cAMP and a series of enzymes to convert an extracellular signal into an intracellular signal.

Answer 10

Adenylate cyclase

Question 11

A phospholipid present in cell membranes. Cleavage of phosphatidylinositol 4,5-bisphosphate releases intracellular signals that activate the phosphoinositide cascade.

Answer 11

Phosphatidylinositol 4,5-biphosphate (PIP2)

Question 12

A receptor tyrosine kinase that mediates the action of insulin.

Answer 12

Insulin receptor

Question 13

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.

Answer 13

Phosphoinositide cascade

Question 14

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.

Answer 14

Insulin-receptor substate (IRS)

Question 15

Proteins that interact with small G proteins that facilitate the exchange of GTP for GDP.

Answer 15

Guanine-nucleotide-exchange factor (GEF)

Question 16

A receptor tyrosine kinase that is activated by epidermal growth factor. The unbound receptor exists as a monomer, but dimerizes upon growth factor binding.

Answer 16

EGF receptor (EGFR)

Question 17

Non-enzymatic proteins that serve to tether the downstream components of a signaling pathway to the membrane.

Answer 17

Adaptor protein

Question 18

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.

Answer 18

Dimerization arm

Question 19

Proteins that interact with GTP-bound small G proteins and facilitate GTP hydrolysis.

Answer 19

GTPase-activating protein (GAP)

Question 20

Intracellular kinases, which are activated by reception of signals from outside the cell, that are members of signal transduction cascades.

Answer 20

Extracellular signal-regulated kinase (ERK)

Question 21

a gene whose expression contributes to the development of cancer.

Answer 21

Oncogene

Question 22

A 6-kd polypeptide that stimulates the growth of epidermal and epithelial cells.

Answer 22

Epidermal growth factor (EGF)

Question 23

This domain binds phosphoinositide and acts with a phosphotyrosine-binding domain to anchor the IRS protein to the insulin receptor and the associated membrane.

Answer 23

pleckstrin homology domain

Question 24

A protein kinase that is activated by the binding of diacylglycerol.

Answer 24

Protein kinase C (PKC)

Question 25

small signal molecules whose concentration is changed in response to a primary messenger

Answer 25

Second messenger

Question 26

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.

Answer 26

Protein kinase A (PKA)

Question 27

A 7 transmembrane helix receptor for epinephrine (adrenaline).

Answer 27

β-adrenergic receptor (β-AR)

Question 28

The photoreceptor of rod cells. It is composed of the protein opsin and the prosthetic group 11-cis-retinal.

Answer 28

Rhodopsin

Question 29

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.

Answer 29

Seven-transmembrane-helix (7TM) receptor

Question 30

the information embodied in the interaction of ligand with its receptor molecule.

Answer 30

Primary messenger

Question 31

A kinase that catalyzes the transfer of a phosphoryl group from ATP to the hydroxyl group of tyrosine.

Answer 31

Tyrosine kinase

Question 32

A kinase that phosphorylates and inactivates the β-adrenergic receptor.

Answer 32

β-adrenergic receptor kinase

Question 33

transmembrane receptor proteins that, when bound to the appropriate signal molecules, display intracellular protein kinase activity, phosphorylating proteins on a tyrosine residue.

Answer 33

Receptor tyrosine kinase

Question 34

domains of approximately 100 amino acids that bind to phosphotyrosine residues.

Answer 34

Src homology 2 (SH2) domain

Question 35

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.

Answer 35

Small G protein

Question 36

Genes for DNA-repair proteins that suppress tumor development when at least one copy of the gene is free of a deleterious mutation.

Answer 36

Tumor-suppressor gene

Question 37

signal transduction proteins that usually regulate cell growth in some fashion. When mutated, these genes become oncogenes and contribute to the development of cancer.

Answer 37

Proto-oncogene

Question 38

domains that bind proline-rich stretches of polypeptide.

Answer 38

Src homology 3 (SH3) domain

Question 39

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.

Answer 39

Ras