Lecture Set 8

Question 1

What are the three ways proteins interact with membranes?

Answer 1

1) Integral –> hydrophobic core regions
2) Peripheral –> non-covalently bound to membrane lipid
3) Lipid-anchored –> covalently bonded to membrane lipids

Question 2

What is the difference between integral/peripheral

Answer 2

functionally: integral can only be removed through detergents
peripheral can be removed by chelation of Ca2+, addition of urea, change in pH or ionic strength

Question 3

What are the four modifications of lipid anchored proteins?

Answer 3

1) palmitation
2) Meristylation
3) prenylation
4) GPI –> glycosylphosphatidylinositol
palmitation and meristylation = acetylation
first three only occur on cytosolic face

Question 4

What are the 4 different types of integral membrane proteins?

Answer 4

type 1 = N-terminal on exoplasmic face
type 2 = C-terminal on exoplasmic face
type 3 = multi-pass protein
type 4 = multiple single pass proteins

Question 5

what does the transmembrane sequence look like?

Answer 5

alpha-helix, hydrophobic, can be a beta-barrel

Question 6

How can you test for protein motility in the membrane?

Answer 6

fluoresence tagging, then combine with a hybrid cell through virus-induced fusion, then watch mixture of fluorescent proteins

Question 7

where are oligosaccaride chains found on proteins?

Answer 7

noncytosolic side

Question 8

How can cell surface protein movement be restricted?

Answer 8

1) attachment to extracellular matrix
2) attach to cell cortex
3) interact with proteins on other cells
4) junctional barriers (ex. tight junctions)