Post Translation Modification of Proteins

Question 1

what does post translation modification do?

Answer 1

converts inactive proteins to active

Question 2

trimming

Answer 2

removing part of polypeptide chain for activation

Question 3

enzyme that trims large precursor molecules

Answer 3

endoproteases

Question 4

intracellular trimming ex

Answer 4

insulin:

preproinsulin -> proinsulin -> insulin

Question 5

extracellular trimming ex

Answer 5

zymogens are activated after they reach site of activation

pepsinogen -> pepsin in stomach
trypsinogen -> trypsin in intestine

Question 6

covalent modification of amino acids can be modified to achieve:

Answer 6

1. alter activity or stability of protein
   2, direct protein to cellular compartment
2. prepare protein for secretion from cell

Question 7

where do covalent modifications take place?

Answer 7

in endoplasmic reticulum and golgi apparatus

Question 8

covalent modifications include:

Answer 8

1. phosphorylation
2. glycosylation
3. acetylation or methylation
4. hydroxylation
5. carboxylation

Question 9

phosphorylation mechanism

Answer 9

addition of phosphate(phosphorylation) by kinase or removal by phosphatase (dephosphorylation)

Question 10

glycosylation

Answer 10

addition of carb to protein forming glycoprotein or proteoglycan

Question 11

o linked glycoprotein

Answer 11

carb is linked to OH group of serine or threonine

Question 12

n linked glycoprotein

Answer 12

carb is linked to amide group os asparagine

Question 13

where is glycosylation common

Answer 13

in proteins that are connected to lysosomes or cell membranes

Question 14

acetylation or methylation

Answer 14

the N terminal (first) amino acid is sometimes acelyated or methylated to change the charge on protein

Question 15

hydroxylation

Answer 15

add OH

Hydroxylation of prolyl and Lysyl residues in collagen to hydroxyl prolyl and hydroxyl lysyl

Question 16

hydroxylation leads to

Answer 16

stabilization of protein

Question 17

carboxylation def and example

Answer 17

adds CO2. converts glutamate to y carboxy glutamate which is important for binding of calcium

Question 18

carboxylation helps in

Answer 18

clotting factors and osteocalcin (bone protein)