Ubiquitination Flashcards
what is ubiquitination?
a non-permanent, reversible PTM via the addition of a ubiquitin molecule to a protein
what is the structure of ubiquitin?
76 residues with 7 key lysine groups
c terminus
groups of added ubiquitins = ubiquitin chain
what is the purpose of ubiquitin chains?
can control which organelle ras interacts with, for example cytosolic proteins which send proteins to proteosome for degradation
what are the two forms of ubiquitin chain conformations?
closed (lysine 48 most common)
extended (lysine 63 most common)
what are canonical non-degradative chains?
lysine 63 ub4 proximal and distal sides 4 ubiquitins linked by lys63 localisation of protein in cell which alters function, is not instructing extended conformation
what are canonical degredative chains?
lys48 ub4
4 ubiquitins linked by lys48
closed conformation
instruct target protein to be transported to proteosome for degradation
what are alternative non-degradative chains?
met1 ub4
open conformation
what are alternative degradative chains?
lys ub4
closed conformation
what is the process of ubiquitination?
ubiquitin bound to E1, then transfered to E2 via transenthaniolaition
e2 interacts with e3 to attach ubiquitin to target
what is E1?
ubiquitin activating enzyme that forms thioester bond between conserved cys and c terminal of ub
what is E2?
ubiquitin conjugating enzyme
activated ub passed to E2 via transthiolation
ubc13-mms2 conjugates k63 chains
ube2k conjugates k48 chains
what is E3?
ubiquitin ligating enzymes
involved in target/substrate protein recognition
transfers activated ubiquitin to target proteins
what are the three families of E3?
HECT (catalytic)
RING (non-catalytic)
ubox (non-catalytic)
what are deubiquitinases?
removal of ubiquitins
what is the26S proteosome?
major role of ubiquitins is to send proteins here
huge protein which chops up and degrades proteins
