3.1

Question 1

Integral protein

Answer 1

-are embedded all the way inside of the cell membrane
-removed with strong chemicals & detergents

Question 2

Peripheral protein

Answer 2

-membrane associated NOT embedded
-interacts with hydrophilic part of membrane (outside) and polar head groups of lipids

Question 3

Anchored protein

Answer 3

-Only the hydrophobic tail on the protein is embedded in the membrane

Question 4

Long chain fatty acids

Answer 4

-palmitoylation on Cys/Ser group
-Myristoylation to amino terminyl Gly

Question 5

Isoprenoids

Answer 5

Prenylation

Question 6

GPI

Answer 6

Phosphodiester bond from carboxynl terminus to a GPI (protein covalently bonded to a membrane lipid headgroup)

Question 7

Amphitropic

Answer 7

-Sometimes associates with the membrane
-is regulated

Question 8

What motif are integral membrane proteins made of?

Answer 8

-Alpha helices
-Ex: rhodopsin

Question 9

Membrane-spanning alpha helices

Answer 9

-Made of 20 hydroPHOBIC residues in a row

Question 10

Hydropathy plot: positive and negative value meanings

Answer 10

-Positive (above line): Hydrophobic
-Negative (below line): Hydrophilic

Question 11

Membrane-spanning beta barrels

Answer 11

-hydrophobic on the outside and hydrophilic on the inside
-hard to predict–>cannot use hydropathy plot–>instead use sequence comparison
-porins are made of beta barrels

Question 12

How many amino acids are membrane-spanning alpha and beta barrels made of?

Answer 12

-Alpha: 20 amino acids
-Beta: 7-9 amino acids

Question 13

What are membrane proteins enriched with?

Answer 13

-Tryptophan and tyrosine residues
-act as interface anchors

Question 14

Positive inside rule

Answer 14

Positively charged residues are on the CYTOPLASMIC side

Question 15

Annular lipids 2 primary functions?

Answer 15

1. Forms a grease seal around proteins in the membrane
2. Stabilizes the protein in the proper orientation in the membrane

Question 16

Lipid rafts/microdomains

Answer 16

-Signaling
-made of cholesterol and sphingolipids
-contains palmitoylated/myristolated proteins that lets acyl tail insert into lipid bilayer

Question 17

Caveolin

Answer 17

-Makes the membrane curve
-binds to cholesterol regions of lipid rafts
-has trafficking and signaling functions

Question 18

What are the 4 domains and functions of caveolin

Answer 18

1. Oligomerization: site of dimerization
2. Scaffolding: links oligomerization and transmembrane domains
3. Transmembrane: 2 helix bundle that transverses the membrane bilayer in cholesterol rich regions
4. Membrane attachment-palmitoyl tails insert in membrane

Question 19

Steps of vesicle fusion

Answer 19

1. Vesicle approach: interacts with membrane through adapter proteins
2. Zipper: v-SNARE, t-SNARE & SNAP25 form a zipper together which contracts alpha helices and pulls them membranes into proximity
3. Membrane hemifusion: Outer leaflets fuse and forms a supermembrane and brings inner leaflets into contact
   4.Formation of fusion pore: Vesicular membrane and plasma membrane fuse and pore opens
4. Release of neurotransmitter to synaptic cleft: Fusion pore widens and releases neurotransmitters