Membrane bound proteins

Question 1

What catalyse the reversible phosphorylation of specific serine, threonine and tyrosine and histidine residues with other proteins?

Answer 1

Kinases (phosphotransferases)

Question 2

What does the resulting change in sterics and electronics affect?

Answer 2

• Protein tertiary & quaternary structure

- Protein-protein interactions

Question 3

What does the resulting change in sterics & electronics lead to?

Answer 3

Modulation of enzymatic activity

Question 4

What are a key target for new anti-cancer drugs?

Answer 4

Kinases

Question 5

What do types I and II differ in?

Answer 5

domain orientation

Question 6

What is the difference between type III and IV?

Answer 6

• Multiple transmembrane helices within a single polypeptide for type III
• Multiple polypeptide chains for type IV

Question 7

What do types V and VI have?

Answer 7

covalent lipid anchors

Question 8

How many turns do most transmembrane helices have?

Answer 8

6-7

Question 9

What does each hexagon reprasent in glycophorin?

Answer 9

Tetrasaccharide

Question 10

What is the function of glycophorin?

Answer 10

Not known

Question 11

What does the loss of sugars result in?

Answer 11

Destruction of red blood cell

Question 12

What does main transmembrane domain (Leu75-Tyr93) consist of?

Answer 12

19 amino acids in an a-helix

Question 13

Is it harder/easier to get high quality structural information for membrane bound proteins than freely soluble ones?

Answer 13

Harder

Question 14

What is the hydropathy of the window at residue 4?

Answer 14

The average of the individual hydropathies of residues 1-7

Question 15

What does the hydropathy at residue 5 window look at?

Answer 15

Residues 2-8

Question 16

What are positive hydropathy windows for 20 residues in a row indicative of?

Answer 16

A transmembrane domain

Question 17

What are found at the water-lipid interface?

Answer 17

• Tryptophan (red, hydropathy - 0.9)

- Tyrosine (orange, hydropathy - 1.3)

Question 18

What are usually found exposed to water?

Answer 18

charged residues (blue)

Question 19

What does helix bundling allow for?

Answer 19

Hydrogen bonding to glucose in channel region

Question 20

What is GLUT1?

Answer 20

A glucose transporter protein

Question 21

What is switching in an e.coli lactose permease?

Answer 21

Due to a change in protonation in Glu325-Arg302 salt bridge according to transmembrane proton gradient

Question 22

What is the calcium pump of sarcoplasmic reticulum?

Answer 22

• Single polypeptide with Mr 100,000

Question 23

Phosphorylation of Asp351 causes what?

Answer 23

• Widespread conformational change, changing exposure face of calcium binding domain

Question 24

What does this conformational change affect?

Answer 24

The affinity for calcium in its binding site allowing release into the lumenal side of the membrane

Question 25

What does the ATP-binding cassette transporters do?

Answer 25

Pump ions, biomolecules and drugs in and out of cells

Question 26

What is the human ABC transporter MDR1 responsible for?

Answer 26

Tumor chemotherapy resistance to drugs such as adriamycin

Question 27

What are microbial ABC transporters targets in?

Answer 27

Design of new antibiotics

Question 28

What is AQP-1 (an aquaporin)?

Answer 28

Tetramer of identical subunits, each subunit has one water permeable pore

Question 29

What is the key amino acid sequence conserved in all aquaporins?

Answer 29

Asm-Pro-Ala (NPA)

Question 30

Arg & His hydrogen bond to ____ but repel _______

Answer 30

water | hydronium

Question 31

What do microbial cells require?

Answer 31

- Maintenance of high concentration gradient of K in order to survive

Question 32

What does the potassium channel consist of?

Answer 32

- 8 transmembrane a-helices (2 each from four subunits) - Cone shape - Discriminates for K based on size & shape

Question 33

What are B-barrel membrane proteins?

Answer 33

Usually 20 or more lines of B-sheet coming together to maximise secondary structure interactions

Question 34

More extended conformation means that a sequence of only __-hydro_____ residues is enough to span a membrane

Answer 34

7 | phobic

Question 35

What does valinomycin (a potassium binding antibiotic) do?

Answer 35

- Selectively binds K via its carbonyl oxygen atoms | - Valine-like side chains allow the complex to pass readily through the bilayer

Question 36

What does this allow for in valinomycin?

Answer 36

The concentration of K either side of the membrane to equilibrate, killing the cell

Question 37

Membrane bound proteins serve as _______ but may also display _________

Answer 37

receptors | enzymatic activity

Question 38

Proteins pass along messages through _____ changes, as in reversible ________ of ______ or through _______ changes

Answer 38

physical phosphorylation kinases conformational

Question 39

What do these changes allow for?

Answer 39

- Changes in shape determine which partner substances are allowed to bind, thus passing on the 'message' - In some cases, the controlled passage of substances into/out of the cell

Question 40

How do certain antibiotics act?

Answer 40

By disrupting the fine control of these processes

Question 41

``` Which of the following amino acids is most likely to be found within a membrane spanning alpha helix facing the membrane itself? A Aspartic Acid B Arginine C Glutamic acid D Lysine E Valine ```

Answer 41

E Valine

Question 42

``` Approximately how many amino acids are required for a membrane spanning alpha-helix? A 5 B 10 C 20 D 40 E 80 ```

Answer 42

C 20

Question 43

``` How many membrane spanning helicies are found in a G-Protein Coupled Receptor (GPCR)? A 1 B 3 C 5 D 7 E 9 ```

Answer 43

D 7