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PHA111 > Membrane bound proteins > Flashcards

Membrane bound proteins Flashcards

1
Q

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

A

Kinases (phosphotransferases)

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2
Q

What does the resulting change in sterics and electronics affect?

A
  • Protein tertiary & quaternary structure

- Protein-protein interactions

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3
Q

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

A

Modulation of enzymatic activity

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4
Q

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

A

Kinases

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5
Q

What do types I and II differ in?

A

domain orientation

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6
Q

What is the difference between type III and IV?

A
  • Multiple transmembrane helices within a single polypeptide for type III
  • Multiple polypeptide chains for type IV
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7
Q

What do types V and VI have?

A

covalent lipid anchors

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8
Q

How many turns do most transmembrane helices have?

A

6-7

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9
Q

What does each hexagon reprasent in glycophorin?

A

Tetrasaccharide

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10
Q

What is the function of glycophorin?

A

Not known

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11
Q

What does the loss of sugars result in?

A

Destruction of red blood cell

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12
Q

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

A

19 amino acids in an a-helix

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13
Q

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

A

Harder

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14
Q

What is the hydropathy of the window at residue 4?

A

The average of the individual hydropathies of residues 1-7

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15
Q

What does the hydropathy at residue 5 window look at?

A

Residues 2-8

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16
Q

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

A

A transmembrane domain

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17
Q

What are found at the water-lipid interface?

A
  • Tryptophan (red, hydropathy - 0.9)

- Tyrosine (orange, hydropathy - 1.3)

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18
Q

What are usually found exposed to water?

A

charged residues (blue)

19
Q

What does helix bundling allow for?

A

Hydrogen bonding to glucose in channel region

20
Q

What is GLUT1?

A

A glucose transporter protein

21
Q

What is switching in an e.coli lactose permease?

A

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

22
Q

What is the calcium pump of sarcoplasmic reticulum?

A
  • Single polypeptide with Mr 100,000
23
Q

Phosphorylation of Asp351 causes what?

A
  • Widespread conformational change, changing exposure face of calcium binding domain
24
Q

What does this conformational change affect?

A

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

25
Q

What does the ATP-binding cassette transporters do?

A

Pump ions, biomolecules and drugs in and out of cells

26
Q

What is the human ABC transporter MDR1 responsible for?

A

Tumor chemotherapy resistance to drugs such as adriamycin

27
Q

What are microbial ABC transporters targets in?

A

Design of new antibiotics

28
Q

What is AQP-1 (an aquaporin)?

A

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

29
Q

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

A

Asm-Pro-Ala (NPA)

30
Q

Arg & His hydrogen bond to ____ but repel _______

A

water

hydronium

31
Q

What do microbial cells require?

A
  • Maintenance of high concentration gradient of K in order to survive
32
Q

What does the potassium channel consist of?

A
  • 8 transmembrane a-helices (2 each from four subunits)
  • Cone shape
  • Discriminates for K based on size & shape
33
Q

What are B-barrel membrane proteins?

A

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

34
Q

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

A

7

phobic

35
Q

What does valinomycin (a potassium binding antibiotic) do?

A
  • Selectively binds K via its carbonyl oxygen atoms

- Valine-like side chains allow the complex to pass readily through the bilayer

36
Q

What does this allow for in valinomycin?

A

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

37
Q

Membrane bound proteins serve as _______ but may also display _________

A

receptors

enzymatic activity

38
Q

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

A

physical
phosphorylation
kinases
conformational

39
Q

What do these changes allow for?

A
  • 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
40
Q

How do certain antibiotics act?

A

By disrupting the fine control of these processes

41
Q 
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
A

E Valine

42
Q 
Approximately how many amino acids are required for a membrane spanning alpha-helix?
	A	5
	B	10
	C	20
	D	40
	E	80
A

C 20

43
Q 
How many membrane spanning helicies are found in a G-Protein Coupled Receptor (GPCR)?
	A	1
B	3
	C	5
	D	7
	E	9
A

D 7

PHA111 (23 decks)

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