Signal Transduction Events

Front 1

Protein Kinases catalyze the transfer of the terminal phosphate group of ATP to which amino acids?

Back 1

Serine, Threonine, and some specific ones do tyrosine.

Front 2

The phosphorylatino of a prootein is only transient and __________ exist that hydroplyse the phospho form back to the dephospho form.

Back 2

protein phosphatases

Front 3

what is the principal way cells use external signals to regulate intracellular metabolic pathways?

Back 3

By altering the phosphorylation state of a protein, i.e. increasing or decreasing the activity of kinases and phosphatases.

Front 4

Of the classes of protein kinases, which three major ones are intracellular and phosphorylate serine or threonine residues of proteins.

Back 4

cAMP-dependent protein kinase A; protein kinase C; Ca/calmodulin dpedendent PK.

Front 5

A family of transmembrane receptors with kinase activity also phosphorylate proteins soley at the tyrosine residue these are called the _________.

Back 5

tyrosine kinases.

Front 6

multipass proteins whose extracellular domains act as receptor sites for lignads and intracellular regions have two separate sites, one that binds G proteins the other that becomes phosphorylated during receptor desensitization.

Back 6

G-protein linked receptors

Front 7

Composed of a large subunit specific functional alpha subunit, beta and gamma subunits.

Back 7

G-protein

Front 8

Name four types of G-proteins.

Back 8

Stimulatory Gs, Inhibitory Gi, phospholipase C activator Gq, and transducin Gt.

Front 9

Describe the steps in the signaling via Gs.

Back 9

A protein signaling molecule binds to the receptor on the E side. This alters the conformation of the receptor which allows the G-alpha unit to exchange the GDP for GTP and becomes activiated. The Activated G-alpha unit travels to adenylate cyclase and activates it. The adenylate cyclase converts ATP to cAMP. The cAMP initiates a number of cellular responses. The G-alpha subunit is deactivated by hydrolyzing the bound GTP to GDP.

Front 10

What deactivates adenylate cyclase?

Back 10

phosphodiesterase

Front 11

cAMP is an intracellular signaling molecule that activates?

Back 11

cAMP dependent protein kinase A; PKA

Front 12

What are the two types of responses PKA can perform?

Back 12

futher phosphorylate other enzymes in the cytosol initiating a cascade of phophorylations and a specific response or travel to the nucleus and phophorylate gene regulatory proteins resulting in the transcription of the requisite genes.

Front 13

What are the two different binding sites on protein kinases?

Back 13

One for ATP and one that recognizes specific amino acids identifying particular proteins for phosphorylation.

Front 14

What are the two major classes of phosphatases?

Back 14

Ones that dephosphatate on the threonine and serine residues and ones for tyrosine residues.

Front 15

What does Gi do?

Back 15

Gi is activated and instead of stimulating adenylate cyclase it inhibits it.

Front 16

An example of a ligand that inactivates a cell via Gi is ?

Back 16

Somatostatin

Front 17

Describe the signaling pathway via the Gq protein.

Back 17

A polypeptide hormone binds activating the Gq protein. Gq activates phospholipase C. Phospholipase C cleaves phosphatidylinositol bisphosphate into inositol triphospate (IP3), leaving diacyl glycerol in the membrane. IP3 travels to organelles opening up calcium channels causing an influx of calcium. DAG also activates protein kinase C which iniates cellular response by phosphorylating target proteins. Calcium acts as a second messenger as well.

Front 18

What is the calcium binding protein in the cytosol? in skeletal and cardiac muscle?

Back 18

calmodulin; troponin C

Front 19

What does calcium do after it has been released into the cytosol?

Back 19

It binds to calmodulin causing a conformational change. The confomrational change leads ca-calmodulin complex to activate target proteins causing a cellular response.

Front 20

The ca-calmodulin complex activates which specific target protein.

Back 20

CAM kinase II

Front 21

What can DAG be turned into from the plasma membrane:

Back 21

arachadonic acid -> prostaglandins

Front 22

single pass transmembrane proteins thatt become enzymatic when activated by an extracellular signal particularly the GROWTH HORMONES.

Back 22

catalytic receptor

Front 23

Describe the activity of an activated catalytic receptor.

Back 23

the activated catalytic domain of the receptor functions by transferring the terminal phosphate group of ATP to the hydroxyl group of tyrosine residues located on other specific target proteins in the cell. This initiates a reaction cascade by phosphorylating other serin-threonine specific kinases in the cytosol that require this modification for their own activity.

Front 24

Catalytic receptors are also referred to as ?

Back 24

tyrosine kinases

Front 25

How do tyrosine kinases get phosphorylated?

Back 25

tyrosine kinases autophosphorylate themselves after becoming activated by a growth factor.