Week 2 Flashcards
P folding signs +denaturation
Signs: hydrophobic patches at surface sign of misfolding
Denaturation by heat or urea… a.a. sequence is enough for renaturation&3-D structure (follwing a folding pathway)
if misfolded=wrong conformation:enzymatic activity=inactive
Chaperons
FAciliatate folding of P by guiding them along FP
PErmit partially misfolded to return to FP
Recognizes exposed hydrophobic patches
Upregulated under condition where misfolded protein accummulate (Ex.: heat-shock)
Chaperone (what do they do)
Fold newly made P into functional conf
REfold mis/unfolded P into funct. conf.
Disassemble potentially toxic P (due to misfolding)
Assemble/Dismantle large multip complex
Mediate trasf. between in/active form of some P
Chaperone work
Work throught ATP-dependant cycles of binding/release from misfolded clien mol.
Block the exposed hydrophobic patches to keep the folding/refolding safe
Molecular chaperones (single mol.) vs chaperonin (multisubunit refolding chamber)
Chaperons essential 4 life
Cell would have a ccrippling burden of misfolded non functional &agrgregate-prones P)
very highly conserved in a.a. sequencethru evolution
ex…Hsp 70: binds to exposed hydrophobic residues of nascent polypeptide+protect from aggregation until properly folded…. cycle of P binding & conf change with AtP binding and hydrolysis
Chaperonins
Hsp 60’s:
form enclosed chamber made up of inward
facing P-binding subunit that undergo concerted ATP-binding hydrolysis and conf. change
Common them:
ATP-binding
ATP hydrolysis
conformational change
binding to the client P
If chaperon can’t fix a P
=destroyed by proteolytic cleavage into small fragments by….
Ubiquitin and proteasome system
Ubiquitin and proteasome system
System that destroy uncorrected misfolded P
Ub is like a tag to signalize the proteasome to destroy
Attach ub to P then make a chain poly-ub to be recognize by proteasome
ubiquitin part expl.
ub: 76 a.a. protein that link covalently to lysin residues on target P
E1–>E2–>E3
E1
take ub and ATP (floating in cytoplasm)…becoming a high-E bomb
AMP+pyrophosphate (ppi)+takes ub and sticks it to one of its side chain (to itself) and then trasnfer it to E2
E2
interacts with E3 to know what to do with the ub…. then ubiquinate the P
E3
Recognize misfolded P or “normal P” that cell need to degrade for regulatory purpose and tells the E2 who’s the target
havea amino gr. on lysine
cyclins triggered by regulated phsophorylation at a specific a.a.
Protease
P in cup recognize and binds to poly-ub by hydrolysis
unfold target (ATP)+ feed them into central chamber (20s core)
20s core subunit form inward-facing proteases:
degrade P to a.a. or short oligopeptides=danger minimized
Mechanism evolved be prokaryote/eukaryote divergence
protease=danger fo9r all becasue destroy P: lot of regulation…chamber=safe Protease can’t get out, P has to be fed to it specificaaly
P quanlity control failure (scale)
Right folded on its own
if not
Chaperones assistance
if not
DEgradation by multiubiquination/proteasome mechanism
if not
P aggregate=bad outcome (can take a lot of time)
