Proteins III

Question 1

What lactate dehydrogenase isoform may be increased in after a myocardial infarction?

Answer 1

H4

Question 2

What carbohydrate structure differs between type A, B and O blood types?

Answer 2

Type A has an extra GalNac and type B has an extra Gal (compared to type O).

Question 3

Which class of cell-surface receptors has 7 transmembrane segments? What is the purpose of this receptor passing into and out of the membrane?

Answer 3

G-Protein Coupled Receptors (GPCR)

Question 4

Which type of glycosylation occurs in both the Rough ER and the golgi?

Answer 4

N-linked (to Asparagine)

Question 5

Which type of glycosylation ONLY occurs in the golgi (where proteins are sorted and marked for its destination.)

Answer 5

• O-linked (to serine)

- O-linked (to 5-Hydroxylysine)

Question 6

Charges, hydrophobicity, and antigenicity may be introduced to a protein via covalent modification after _______.

Answer 6

Translation (Post-translational modification)

Question 7

Almost ALL modifications post-translation are added due to enzymes (thus are not spontaneous), EXCEPT _______?

Answer 7

HbAIC formation

Question 8

Glycosidic addition usually occurs on what two types of proteins?

Answer 8

• Membrane proteins

- Secretory proteins

Question 9

Name 3 of the physiological roles of glycosylation in glycoproteins.

Answer 9

1) Folding of transmembrane proteins
2) Stability
3) Recognition/cell adhesion

Question 10

What post-translational process helps promote resistance to degradation in a cell. (eg. the lysine residues on Histone H3 which reduce affinity for DNA.)

Answer 10

Acetylation

Question 11

Which enzyme catalyzes the attachment of an acetyl group to histone?

Answer 11

Histone acetyl-transferase

Question 12

Which enzyme catalyzes the removal of an acetyl group to histone?

Answer 12

Histone de-acetylase

Question 13

What three ways can proteins be anchored to cell membranes?

Answer 13

1) Acetylation (to N-terminal Glycine)
2) Prenylation (to C-terminal Cysteine)
3) GPI Anchor (to C-terminus)

Question 14

What anchors alpha and beta-gamma subunits of of G-proteins and what does this anchoring allow G-proteins to do along the cytoplasmic membrane?

Answer 14

• Myristoyl and geranylgeranyl

- Translocate

Question 15

In addition to acetlyation and prenylation, name the 4 other forms of post-translational modification via enzymatic addition.

Answer 15

1) Phosphorylation
2) Hydroxylation
3) Carboxylation
4) Methylation

Question 16

Name the 3 types of membrane associated proteins.

Answer 16

1) Transmembrane (integral)
2) Peripheral
3) Lipid anchored

Question 17

Cellular membranes are about ___ anxtrums (A) wide which is equivalent to an alpha-helix about ____ amino acids long.

Answer 17

• 30

- 20

Question 18

A _____ _____ is used as a prediction of the membrane spanning segments of transmembrane proteins.

Answer 18

Hydropathy plot

Question 19

Explain I-Cell Disease

Answer 19

During post translational modification, mannose fails to be phosphorylated, thus lysosomal enzymes are not delivered to the lysosome. With these enzymes, inclusions of undigested glycosaminoglycans and glycolipids build within the cell (also known as Mucolipidosis Type II).

Question 20

Name 5 chemical denaturants of proteins.

Answer 20

1) 8 M Urea
2) 6 M guanidine HCL
3) Sodium dodecyl sulfate (SDS)
4) Heat
5) pH extremes

Question 21

_____ helps fold proteins that won’t fold spontaneoulsy. What does irreversible protein folding in vivo lead to?

Answer 21

• Chaperones

- Amyloidoses (amyloid plaque buildup)