Glycosylation 1

Question 1

How is a hexane formed?

Answer 1

Hydroxyl group reacts with an aldehyde group to form a sugar ring

Question 2

In a beta glucose is the hydroxyl group projected up or down on carbon 1?

Answer 2

up

Question 3

In a alpha glucose is the hydroxyl group projected up or down on carbon 1?

Answer 3

down

Question 4

What is a epimer?

Answer 4

Differ from glucose by one chiral position.

All derived from glucose

Question 5

What does epimerisation at c4 of glucose form?

Answer 5

Galactose

Question 6

Addition of amino acid group to D-galactose forms what?

Answer 6

GalNAC

Question 7

What is sialic acid?

Answer 7

The name for N-acetylneuraminic acid (NeuAc)

Question 8

Are sugar monomers added as precursors?

Answer 8

Glycosidic bond formation is not spontaneous (energetically favourable) hence activated monomers are used

Question 9

What are sugar monomer precursors activated with ?

Answer 9

UDP- sugar

energy provided by two ATPs consumed to form UDP-sugar

Question 10

What residue are N-linked glycans built on?

Answer 10

asparagine

Question 11

What is yeast N-linked glycosylation pattern like?

Answer 11

High mannose sugar

Question 12

What is Insects N-linked glycosylation pattern like?

Answer 12

Low amounts of mannose

Question 13

What is Plants N-linked glycosylation pattern like?

Answer 13

Complex sugars

Similar to humans but have additional xylose

Question 14

What is mammals N-linked glycosylation pattern like?

Answer 14

Similar to human

Some bisecting glcNAC when branching is not extended

Question 15

What is human N-linked glycosylation pattern like?

Answer 15

Only main difference from mammalian sugars is that the terminal Salic is different by one hydroxyl

Question 16

Which are longer, O-linked or N-linked?

Answer 16

O-linked

Can be used to push receptors above the fuzzy glycan layer

Question 17

Name some intrinsic function of gylcans.

Answer 17

Providing structural components

Modifying protein properties (solubility, stability)

Question 18

Name some extrinsic function of glycans.

Answer 18

Directing trafficking
mediating cell adhesion
mediating signalling

Question 19

What is the affect of HIV proteins glycosylation by host cells?

Answer 19

Protein are recognised as self

Question 20

What is special about alpha-L-iduronidase?

Answer 20

Uses its own N-glycan as a substrate binding and catalytic module

Question 21

How does a peptide enter the lumen of the ER?

Answer 21

Threaded through the membrane into the lumen translationally

Question 22

What is the oligosaccharide precursor built on?

Answer 22

dolichol

Question 23

How many mannoses are removed in the ER?

Answer 23

1

Question 24

How many mannoses are the sugars trimmed back to in the golgi?

Answer 24

5

Question 25

Describe the dolichol.

Answer 25

phospholipid with large with large isoprene

Question 26

How does flippase work?

Answer 26

not known

Question 27

Additions of N-linked sugars are co or post translational?

Answer 27

Co-translational

Question 28

Describe the quality control pathway in the ER?

Answer 28

Proteins enter the ER with 3 Glucoses. This is trimmed back to 1 so the protein can be recognized by calnexin. Glucosidase cleaves the last glucose. If normally folded it leaves the ER. If incorrectly foled it binds a chaperone and a glucose is readded and it re-cycles. Removed for degradation if has spent to long in ER and mannosidase has removed a mannoses.

Question 29

What is the specificity of PNGase?

Answer 29

Cuts between Asn and first sugar

Question 30

What is the main method of glycan analysis?

Answer 30

MALDI mass spec

Question 31

How would you determine glycan structure in a mixture of glycans?

Answer 31

Sequentially add enzymes that target different end sugars and note which peaks move until they share one singular peak i.e. main chain is the same

Question 32

What is the specificity of EndoH?

Answer 32

Cuts between first and second sugar of high mannose glycans

Question 33

Why can EndoH be used to distinguish between secreted and non-secreted protein?

Answer 33

high mannose normally means not secreted

Question 34

The sugars are primarily stereoisomers and will have the same mass. How do you distinguish between them in a mass spec?

Answer 34

By prior knowledge to assign peaks

Question 35

NMR can be used to give 3D structures of glycans. True or false?

Answer 35

true