Glycoproteins (N-glycans) Flashcards

1
Q

O-glycanprotein

A

linked to a polypeptide chain through an O-glycosidic linkage

Most common: alpha-glycosidic linkage between

N-acetylgalactosamine and serine/threonine on a peptide chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

N-linked glycoprotein

A

Beta-N-glycosidic linkage between

N-acetylglucosamine and Asn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Two types of N-linked glycosylation

A

High mannose
- only N-acetylglucosamine and Mannose

Complex type

  • Gal and sialic acid
  • N-acetylglucosamine and mannose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

High Mannose sugar chain characteristics

A

In order…

Asn residue

GlcNAc (beta linkage)

GlcNAc (“)

Mannose (“)

…several peripheral mannose residues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Complex type (acidic) sugar chain characteristics

A

N-acetylglucosamine + galactose + sialic acid

At the peripheral positions of the sugar chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What consensus sequence is the Asn residue always next to?

A

-X-Ser/Thr-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where does assembly and processing of N-glycans take place

A

ER and golgi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

3 general steps of making a N-glycan

A
  1. Assembly of a high mannose type sugar chain on the lipid carrier DOLICHOL PHOSPHATE
  2. Transfer of the high mannose chain from DP —> Asn residue of a nascent peptide chain
  3. Processing of the high mannose —> complex chain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is the Dolichol phosphate located

A

Embedded in the ER membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

More detail of the first step of N-gylcan synthesis

A

(Making high mannose type)

Add residues step-wise

Each step needs a glycosyltransferase and a glycosyl donor

The addition of 3 glucose residues at the end of one of the peripheral Mannoses —> signals the chain is complete

Now it can be transferred to the Asn residue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Processing the high mannose —> complex

A

ER and golgi

***NEED glycosidases to remove the glucose and mannose residues from the peripheral positions of the high mannose sugar

In tandem…need glycosyltransferases with proper sugar donors to add

N-acetylglucoamine, Gal, and Sialic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly