protein mod and cell regulation 1 Flashcards
different proteins have
different half lifes
structure of ubiquitin
76aa heat stable highly conserved -all aa essential wide spread distribution glycine at C-terminus lysine at 48
E1 what is it
ubiquitin activating enzyme (ATP)
E2 what is it
ubiquitin conjugating enzyme
E3 what is it
ubiquitin protein ligase
how are teh ubiquitins added to one another
lysine 48 to carboxyl group of C-terminal glycine
structure of the proteasome the multienzyme
26s
core has 20s of 28 subunits
4 rings with 7 units ABBA
catalytic activity comes from
beta subunits
cap of 19s does what
recognises 4 UB
has ATPase activity for protein unfolding
core beta subunits have
3 different protease activities
prodcing peptides of 7-9 aa
the core also has
iso-peptidase activity
which cleaves the UB off the peptide
what can actually be degraded
incorrectly synthesised proteins
ageing proteins
regulatory proteins with short half lives
regulatory p after phosphorylation
incorrectly synthesised proteins why
normal protein synthesis is a rapid process and contains errors
about 30%
ageing proteins why
results of damage while functioning within the cell
these proteins must show conformational changes - ubiquitination
short half life proteins why
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
processes regulated by protein degradation
gene transcription cell-cycle control inflammatory response tumour suppression antigen processing
cell cycle control
cyclin B what does it do
promotes mitosis and is synthesised continuously through the cell life
cell cycle control
what happens to cyclin b at anaphase
levels drop to allow mitosis
dues to association to anaphase promoting complex APC
and poly-UB mo of mitosis cyclin
what is APC is a
E3 ligase
which recognises a specific N-terminal 9AA
conserved in the cyclin family (destruction box)
regulation of APC
its active in CDH1 complexes
phosphorylation of CDH1 by cyclin dependent kinase CDK during G1 results in CDH1 dissociation from APC causing inactivation
other roles of uB number 1
ubinated Hrs directs cargo into vesicle buds and recruits cytosolic ESCRT complex to the membrane
other roles of uB number 2
after ESCRT/Hrs complex membrane fuses and pinches of the vesicle
other roles of uB number 3
they are disassembled via AAA-ATPase Vps4 and returned to the cytosol
monoubiquitination is highjacked by HIV for budding
facts about HIV
enveloped retrovirus
requires -4000 gag proteins for virion
monoubiquitination is highjacked by HIV for budding
how does it do it
N-terminal Gag domain interacts with membrane
c-terminal gag required for budding
Tsg101 (part of ESCRT) interacts with C terminus of gag
differences in ub binding
left
lys-48
linked di-ubiquitin in complex with ub binding domain
forms sandwich structure recognising 1 UBD using 2 hydrophobic patches on UB
differences in ub binding
right
lys-63
linked di-ub in complex with 2 UBD
