Lecture 6 - Folding accessory proteins

Question 1

Proteins often fold in vitro into

Answer 1

quasi-stable non-native conformations

Question 2

3 types of accessory proteins

Answer 2

1. Protein disulfide isomerases (PDI)
2. Peptidyl prolyl cis-trans isomerases (PPI)
3. Molecular chaperones

Question 3

When reduced, PDI catalyzes

Answer 3

disulfide interchange reactions

Question 4

PDI shuffles disulfide bonds until

Answer 4

they achieve their native conformation

Question 5

Oxidative PDI serves to

Answer 5

introduce new disulfide bonds into folding proteins

Question 6

_____% of folded proteins contain proline in the cis conformation

Answer 6

10

Question 7

PPIs catalyze

Answer 7

the interconversion of proline from trans to cis

Question 8

Newly synthesized and unfolded proteins contain many exposed

Answer 8

hydrophobic groups

Question 9

Exposed hydrophobic groups in newly synthesized and unfolded proteins are prone to

Answer 9

aggregation and improper folding

Question 10

Molecular chaperones function to

Answer 10

prevent or reverse improper folding and/or aggregation

Question 11

Molecular chaperones work by binding to

Answer 11

exposed hydrophobic groups of an unfolded protein

Question 12

Heat shock protein (Hsp) 70 facilitates

Answer 12

folding of proteins as they are being synthesized by the ribosome

Question 13

Chaperonins are

Answer 13

large multisubunit proteins that bind hydrophobic patches of partly or improperly folded proteins

Question 14

A folding protein is enveloped by the chaperonin, thereby protecting it from

Answer 14

aggregation

Question 15

Chaperonins consist of 2 families

Answer 15

1. Hsp60 (GroEL)
2. Hsp10 (GreES)

Question 16

GroEL has _____ identical subunits

Answer 16

14

Question 17

GroEL has _____ symmetry

Answer 17

D7

Question 18

GroES forms a dome with _____ identical subunits

Answer 18

7

Question 19

GroES has ______ symmetry

Answer 19

C7

Question 20

When GroES caps GroEL, a change in the cis ring of GroEL changes the

Answer 20

volume of the interior

Question 21

If the folding polypeptide does not reach the native state after interacting with GroEL/ES, it can

Answer 21

bind to GroEL again

Question 22

A native protein doesn’t bind to GroEL because

Answer 22

a native protein lacks exposed hydrophobic groups

Question 23

A partly folded polypeptide intermediate is trapped in a local energy minimum, and binding to GroEL

Answer 23

raises its free energy so it can reach the global energy minimum (native state)