protein mod and cell regulation 1

Question 1

different proteins have

Answer 1

different half lifes

Question 2

structure of ubiquitin

Answer 2

76aa
heat stable 
highly conserved -all aa essential 
wide spread distribution 
glycine at C-terminus
lysine at 48

Question 3

E1 what is it

Answer 3

ubiquitin activating enzyme (ATP)

Question 4

E2 what is it

Answer 4

ubiquitin conjugating enzyme

Question 5

E3 what is it

Answer 5

ubiquitin protein ligase

Question 6

how are teh ubiquitins added to one another

Answer 6

lysine 48 to carboxyl group of C-terminal glycine

Question 7

structure of the proteasome the multienzyme

Answer 7

26s
core has 20s of 28 subunits
4 rings with 7 units ABBA

Question 8

catalytic activity comes from

Answer 8

beta subunits

Question 9

cap of 19s does what

Answer 9

recognises 4 UB

has ATPase activity for protein unfolding

Question 10

core beta subunits have

Answer 10

3 different protease activities

prodcing peptides of 7-9 aa

Question 11

the core also has

Answer 11

iso-peptidase activity

which cleaves the UB off the peptide

Question 12

what can actually be degraded

Answer 12

incorrectly synthesised proteins
ageing proteins
regulatory proteins with short half lives
regulatory p after phosphorylation

Question 13

incorrectly synthesised proteins why

Answer 13

normal protein synthesis is a rapid process and contains errors
about 30%

Question 14

ageing proteins why

Answer 14

results of damage while functioning within the cell

these proteins must show conformational changes - ubiquitination

Question 15

short half life proteins why

Answer 15

require rapid degradation
recognition: N-ter sequence affects half life
ie gly have 20+ h while lys is few mins
PEST sequence also marks for degradation

Question 16

processes regulated by protein degradation

Answer 16

gene transcription 
cell-cycle control
inflammatory response 
tumour suppression 
antigen processing

Question 17

cell cycle control

cyclin B what does it do

Answer 17

promotes mitosis and is synthesised continuously through the cell life

Question 18

cell cycle control

what happens to cyclin b at anaphase

Answer 18

levels drop to allow mitosis
dues to association to anaphase promoting complex APC
and poly-UB mo of mitosis cyclin

Question 19

what is APC is a

Answer 19

E3 ligase
which recognises a specific N-terminal 9AA
conserved in the cyclin family (destruction box)

Question 20

regulation of APC

Answer 20

its active in CDH1 complexes
phosphorylation of CDH1 by cyclin dependent kinase CDK during G1 results in CDH1 dissociation from APC causing inactivation

Question 21

other roles of uB number 1

Answer 21

ubinated Hrs directs cargo into vesicle buds and recruits cytosolic ESCRT complex to the membrane

Question 22

other roles of uB number 2

Answer 22

after ESCRT/Hrs complex membrane fuses and pinches of the vesicle

Question 23

other roles of uB number 3

Answer 23

they are disassembled via AAA-ATPase Vps4 and returned to the cytosol

Question 24

monoubiquitination is highjacked by HIV for budding

facts about HIV

Answer 24

enveloped retrovirus

requires -4000 gag proteins for virion

Question 25

monoubiquitination is highjacked by HIV for budding

how does it do it

Answer 25

N-terminal Gag domain interacts with membrane
c-terminal gag required for budding
Tsg101 (part of ESCRT) interacts with C terminus of gag

Question 26

differences in ub binding

left

Answer 26

lys-48
linked di-ubiquitin in complex with ub binding domain
forms sandwich structure recognising 1 UBD using 2 hydrophobic patches on UB

Question 27

differences in ub binding

right

Answer 27

lys-63

linked di-ub in complex with 2 UBD