Protein Processing

Question 1

How does streptomycin block translation?

Answer 1

inhibits initiation by binding 30S subunit of ribosome (prok)

Question 2

How does Shiga & Ricin toxin block translation?

Answer 2

inhibits elongation by binding 60S subunit of ribosome (Euks)…aminoacyl tRNA can’t enter

Question 3

How do clindamycin & erythromycin block translation?

Answer 3

inhibit elongation by binding 50S subunit of ribosome (disrupts translocation in prok)

Question 4

How does tetracycline block translation?

Answer 4

inhibits elongation by binding to 30S subunit of ribosomes so aminoacyl-tRNA can’t enter (prok)

Question 5

What is housed in the large subunit of ribosomes in both prok & euk?

Answer 5

peptidyl transferase activity

Question 6

How does diptheria toxin block translation?

Answer 6

inactivates EF2-GTP & inhibits elongation (stops protein synthesis b/c missing elongation factor to power ribosome translocation)

Question 7

How does chloramphenicol block translation?

Answer 7

inhibits peptidyl transferase activity (of large ribosome subunit in prok)…blocks peptide bond formation

Question 8

How does cycloheximide block translation?

Answer 8

in euk, inhibits peptidyl transferase so not peptide bond formation

Question 9

How does puromycin block translation?

Answer 9

in both prok & euk, cause premature chain termination, resembles normal 3’ end so can enter A site but resistant to hydrolysis & stops ribosome function

Question 10

cytoplasmic pathway for proteins

Answer 10

cytosol, mitochondria, nucleus, peroxisomes

Question 11

secretory pathway for proteins

Answer 11

ER, lyosomes, plasma membrane, secretion

Question 12

signal for lysosome

Answer 12

Mann6-P

Question 13

signal for secretion

Answer 13

Trp-rich domain

Question 14

signal for plasma membrane

Answer 14

N-terminal apolar seq

Question 15

signal for mitochondria

Answer 15

N-terminal hydrophobic alpha helix

Question 16

signal for nucleus

Answer 16

KKKRK (lots of Lys & Arg)

Question 17

signal for ER

Answer 17

KDEL (lots of Lys, Asp, Glu, Leu)

Question 18

signal for peroxisome

Answer 18

SKL

Question 19

I-cell disease

Answer 19

can’t tag proteins w/ Mann6P so can’t get to lysosome, buildup of lysosomal enzymes in plasma!

Question 20

What do chaperones do?

Answer 20

help w/ protein folding for large proteins so can get into proper 3 structure

Question 21

What is proteolytic cleavage?

Answer 21

post translation processing that converts inactive forms of protein enzyme to its active form

Question 22

Acetylation

Answer 22

adds NH3 to Lys residue

get acetyl from acetyl CoA (important role for histones, if add acetyl group then makes less positive & opens up for gene transcription)

Question 23

Glycosylation

Answer 23

adds OH to Ser/Thr or CONH2 to Asn/Gln

important for extracell proteins (usually found on cell surface)

Question 24

Phosphorylation

Answer 24

adds PO4 via ester bond, OH on Ser/Tyr/Thr/Asp & His residue

important for proteins w/ enzyme functions involved in protein kinase cascades (cell growth/differentiation)

Question 25

Disulfide bonds

Answer 25

add SH (to get -S- linkage) to Cys residue

important for protein stability

Question 26

What can result from issues of defective PTM on collagen?

Answer 26

affects collagen assembly can lead to diseases w/ overflexible joints or rupture of blood vessels/intestines

Question 27

What is the risk of defects in protein folding?

Answer 27

neurodegenerative diseases (Alzheimers, Parkinson’s, Huntington’s, Creutzfeld)