1) When Regulation Goes Wrong (CTX & PTX)

Question 1

What 2 Toxins are being focused on?

Answer 1

Cholera toxin & Pertussis toxin

Question 2

What pathogen secretes Cholera toxin CTX?

Answer 2

Vibrio Cholerae

Question 3

What pathogen secretes Perstussis PTX?

Answer 3

Bordetella

Question 4

Where does colonisation of CTX occur?

Answer 4

small intestine

Question 5

What cells actively secrete electrolytes ?

Answer 5

Crypt cells , line intestinal epithelium

Question 6

What is the receptor that allows passage of Cl- into intestinal lumen?

Answer 6

CFTR

Question 7

What type of receptor do crypt cells activate ?

Answer 7

G-protein coupled receptors

Question 8

What activates the CFTR ?

Answer 8

activation of adenyl cyclases and increases cAMP levels

Question 9

What does increased Cl- in lumen create?

Answer 9

electrical potential, attracts Na+

Question 10

How do Na+ travel into lumen? What kind of junctions?

Answer 10

tight junctions

Question 11

Where does the NaCl accumulate?

Answer 11

Gastrial intestinal lumen

Question 12

What is the result of NaCl in lumen?

Answer 12

creates an osmotic gradient across tight junction so water is drawn into gut lumen.

Question 13

What subunits make CTX?

Answer 13

a-b type toxin
2 alpha (1&2) subs and 5 beta subs

Question 14

What does the alpha 1 subunit do in the cell?

Answer 14

increases adenyl cyclase activity and increases cAMP

Question 15

What does the CTX travel through

Answer 15

golgiac apparatus into lumen of endoplasmic rectilium

Question 16

Effect of increased cAMP levels?

Answer 16

excessive secretion of Cl-, CO3- & H20

Question 17

What catalyses the increased cAMP reaction?

Answer 17

Alpha 1 subunit

Question 18

What does CTA1 catalyse?

Answer 18

ADP-ribosylation the Argentine residue present in the G-alpha-s protein

Question 19

What is the source of the ADP-ribose?

Answer 19

NAD

Question 20

What activates the allosteric CTA1 protein?

Answer 20

On one side; NAD-RNA-ribose

On the other; ARF6 (Co-activator)

Question 21

What becomes cleaved on the CTA1 protein?

Answer 21

N-glycosidic bond of the Nicitinomide and ADP- ribiose

Question 22

What occurs when the G-alpha-s is rybosylated?

Answer 22

the arg residue is irreversibly modified by addition of ADP-ribosyl group from NAD+
G-alpha-s can bind GTP but cannot hydrolyse it
increase cAMP.

Question 23

What does PTX invade?

Answer 23

respiratory system
settle in bronchioles of or trachea
cilia stuck together my adhesion molecules

Question 24

What subunits does PTX have?

Answer 24

1 alpha and 5 beta

Question 25

What alpha subunit is involved in PTX?

Answer 25

G-alpha-i

Question 26

What subunit binds to receptor on epithelial cells?

Answer 26

Beta

Question 27

What subunits are endocytosed by receptor ?

Answer 27

the whole molecule

Question 28

What is the fate of the alpha subunit in PTX?

Answer 28

transferred from golgi to ER, dissociates from pentamer, alpha transported to cytosol…

Question 29

what the effect PTX alpha subunit on G-alpha-i ?

Answer 29

It RNA-ribosylates the G-alpha-i, locks into inactive state (GDP- bound form). Can’t inhibit adenyl cyclase, increase cAMP.

Question 30

What is a way to describe G-alpha-protein complexes?

Answer 30

Heterotrimeric