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Biotechnology > Glycosylation 1 > Flashcards

Glycosylation 1 Flashcards

1
Q

How is a hexane formed?

A

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

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2
Q

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

A

up

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3
Q

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

A

down

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4
Q

What is a epimer?

A

Differ from glucose by one chiral position.

All derived from glucose

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5
Q

What does epimerisation at c4 of glucose form?

A

Galactose

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6
Q

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

A

GalNAC

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7
Q

What is sialic acid?

A

The name for N-acetylneuraminic acid (NeuAc)

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8
Q

Are sugar monomers added as precursors?

A

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

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9
Q

What are sugar monomer precursors activated with ?

A

UDP- sugar

energy provided by two ATPs consumed to form UDP-sugar

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10
Q

What residue are N-linked glycans built on?

A

asparagine

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11
Q

What is yeast N-linked glycosylation pattern like?

A

High mannose sugar

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12
Q

What is Insects N-linked glycosylation pattern like?

A

Low amounts of mannose

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13
Q

What is Plants N-linked glycosylation pattern like?

A

Complex sugars

Similar to humans but have additional xylose

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14
Q

What is mammals N-linked glycosylation pattern like?

A

Similar to human

Some bisecting glcNAC when branching is not extended

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15
Q

What is human N-linked glycosylation pattern like?

A

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

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16
Q

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

A

O-linked

Can be used to push receptors above the fuzzy glycan layer

17
Q

Name some intrinsic function of gylcans.

A

Providing structural components

Modifying protein properties (solubility, stability)

18
Q

Name some extrinsic function of glycans.

A

Directing trafficking
mediating cell adhesion
mediating signalling

19
Q

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

A

Protein are recognised as self

20
Q

What is special about alpha-L-iduronidase?

A

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

21
Q

How does a peptide enter the lumen of the ER?

A

Threaded through the membrane into the lumen translationally

22
Q

What is the oligosaccharide precursor built on?

A

dolichol

23
Q

How many mannoses are removed in the ER?

A

1

24
Q

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

A

5

25
Q

Describe the dolichol.

A

phospholipid with large with large isoprene

26
Q

How does flippase work?

A

not known

27
Q

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

A

Co-translational

28
Q

Describe the quality control pathway in the ER?

A

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.

29
Q

What is the specificity of PNGase?

A

Cuts between Asn and first sugar

30
Q

What is the main method of glycan analysis?

A

MALDI mass spec

31
Q

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

A

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

32
Q

What is the specificity of EndoH?

A

Cuts between first and second sugar of high mannose glycans

33
Q

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

A

high mannose normally means not secreted

34
Q

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

A

By prior knowledge to assign peaks

35
Q

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

A

true

Biotechnology (13 decks)

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