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BIBC 100 > Receptors > Flashcards

Receptors Flashcards

1
Q

basic signal transduction pathway

A

Signal outside cell is recognized, signal transmitted across membrane, cell elicits response (usually cascades of enzymes)

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2
Q

5 features of signal transduction systems

A

Specificity, Amplification, Modularity, Desensitization/Adaptation, Integration

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3
Q

Specificity

A

signal molec is specific to receptor

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4
Q

Amplification

A

enzyme affects enzymes -> number of affected molecules increases geometrically in cascade

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5
Q

Modularity

A

proteins can have multiple signals converge on them (dampen/strengthen signal), forms diverse signaling complexes

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6
Q

Desensitization/Adaptation

A

feedback inhibition, shuts off receptor or removes it from cell surface

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7
Q

Integration

A

mult signals affect mult receptors, the regularity outcome results from the integrated input from both receptors (either additive or inhibitive)

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8
Q

3 families of membrane bound signal transduction receptor molecules

A

ion channel linked receptors, G protein linked receptors, enzyme linked receptors

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9
Q

3 domains of G protein linked receptors and enzyme linked receptors

A

extracellular domain, transmembrane domain, intracelluar domain

(Tooze 251)

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10
Q

purpose of a membrane receptor’s extracellular domain

A

signal recognition

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11
Q

purpose of a membrane receptor’s transmembrane domain

A

signal transmission

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12
Q

purpose of a membrane receptor’s intracelluar domain

A

signal response and amplification

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13
Q

G proteins

A

bind guanaine nucleotides, act as molecular switches, activated by binding to GTP, inactivated when GTP hydrolyzed to GDP

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14
Q

How is the hydrolysis of GTP catalyzed?

A

done by the G protein itself (but does not turn itself off w/out help since it is a slow GTPase)

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15
Q

How is G protein turned off?

A

G protein itself is a slow GTPase, accelerated w/RGS
(regulators of GTP hydrolysis), binds to active G protein, incr rate of GTP hydrolysis

once hydrolyzed, α unit rebinds to beta-gamma unit

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16
Q

G protein structure

A

most are heterotrimers (α, ß, γ subunits) attached to the cytosolic domain, alpha and gamma bound to membrane by lipids, beta not bound but is always complexed with gamma

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17
Q

Which G protein subunit contains GTPase activity?

A

alpha subunit

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18
Q

How does G protein break into subunits?

A

heterotrimer will dissociate into the alpha subunit and the beta-gamma heterodimer, each indep transmit the signal they received from the same receptor, move onto dif effectors

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19
Q

characteristics of membrane receptors that control the senses/other main physiological responses (GPCR’s)

A

contain 7 transmembrane helices, signals amplified by G proteins

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20
Q

How is G protein turned on?

A

ligand binds to extracelluar domain, receptor undergoes confirmational change, activates cytosolic domain, catalyzes GDP switching for GTP, G protein activated, released, dissociates

22
Q

How are secondary messengers produced?

A

active Gα-GTP complexed with effector molec, triggers production of secondary messengers

23
Q

Ras proteins

A

GTP binding protein, regulators of signal transduction processes leading to cell multiplication and differentiation, molecular switches activated w/protein tyrosine kinase receptors, activity depends on GTP/GDP

23
Q

How to turn off Ras proteins?

A

switched off w/GAP (GTPase activating protein), turns off very slowly w/out GAP

24
Q

RAS structure

A

6 B sheets (5 are parallel), 5 A helices surround sheet

25
Q

receptor tyrosine kinases

A

catalyzes the transfer of phosphate groups to tyrosine, comes together to form a dimer, activates the Tyr groups (ready to transfer P groups )

26
Q

How do receptor tyrosine kinases cause celluar response?

A

relay proteins bind to P groups on Tyr, one responses for each relay protein that binds to P group

27
Q

Cholera toxin

A

failure to turn off GTP-activated Gα, binds to Gα, prevents GTP hydrolysis, can’t stop signaling, results in continued sodium/water excretion to gut

28
Q

What leads to uncontrollable cell growth?

A

RAS mutated, can’t be activated to turn off GTP-activated Gα, prevents GTP hydrolysis, can’t stop signaling

29
Q

RAS binding pocket structure

A

loop regions binding the B strands and A helices

30
Q

Where is GTP bound in RAS?

A

pocket at the C-term of B strands

31
Q

RAS and Gα use MG2+ ions for what?

A

stabilize guanine nucleotide complex, weaken P-O that gets split for catalysis

32
Q

Why does RAS take so long to hydrolyze GTP w/out GAP?

A

lacks the Arg that stabilizes the negative charge on the phosphate, GAP supplies the necessary Arg

33
Q

transducin

A

G protein that mediates light adaptation in retinal rods

34
Q

phosducin purpose

A

G protein regulator molecule, reduces transducin sensitivity, blocks Gα binding site, binds Gß and pulls it into the cytoplasm where it is inactive

35
Q

Rhodopsin mech

A

Receptor (rhodopsin) absorbs photons, activates G-protein (transducin), which activates cGMP phosophodiesterase, degrades cGMP to GMP

36
Q

Gß structure

A

7 stranded B propeller, each blade is 4 antiparallel B sheet

37
Q

Gγ structure

A

A helix, stabilized by Gß

Tooze 263

38
Q

Gα structure

A

3 switch regions

39
Q

6 general types of signal transducers

A

G protein coupled receptors, receptor tyrosine kinases, receptor guanylyl cyclases, gated ion channels, adhesion receptors, nuclear recptors

40
Q

eg of G protein coupled receptors

A

Ras, ß-adrenergic receptor

41
Q

eg of receptor tyrosine kinases

A

insulin receptor, growth hormone, epidermal growth factor receptor

42
Q

eg of gated ion channels

A

voltage gated K+ channels, nAChR

43
Q

how are G proteins efficient?

A

can be amplified at 2 steps:

active receptor can activate mult G proteins

each downstream target can produce many secondary messengers

44
Q

ß-adrenergic receptor

A

ligand: epinephrine
receptor: ß-adrenergic receptor
effector: adenylate cyclase
secondary messenger: cycle AMP
response: glycogen breakdown (cAMP activates protein kinase A)

45
Q

Human Growth Hormone structure

A

4 helix bundle; up, up, down, down

46
Q

domains of hormone receptors

A

3 domains: EC ligand binding domain, single transmembrane domain, IC domain

47
Q

Human Growth Hormone Receptor structure

A

consists of just the EC domain, 2 immunoglobulin-like chains, two forms dimer, 4 sets of 7

(Tooze 267)

48
Q

How does the Human Growth Hormone dimerize?

A

occurs sequentially, cross phosphorylation: GH binds to 1st subunit which brings the 2nd subunit together, aided by noncatalytic proteins that hold together other protein molec

49
Q

Cross talk

A

ß adrenergic receptor “talks” to the insulin receptor

BIBC 100 (8 decks)

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