Protein folding

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Protein folding
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James Dewey Wason Francis Harry Compton Crick
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DNA RNA Proein
?
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proteomics
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(No Transcript)
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Protein folding live
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? ? 1893,11,24---1959,8,8
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1912????????????????????,???????????????????????
?,2???????1916???,???????,?????????1917???????????
?,??????????? Folin??????,?????????1924?????????
????,1931??????????????????????????????
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ribonuclease
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Some denatured proteins can be renatured
Anfinsen?? 1961
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Probability that correct folding would occur in
ribonuclease
given that there are 8 cysteine residues 1/7 x
1/5 x 1/3 x 1 1/105
expected activity 1
observed activity was 100
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Mechanisms to explain re-folding Factors
driving protein folding

• 2n torsion angles can have 32n 10n possible
  conformations

• if n 100, then number of conformations, 10100

• if one conformation is explored every 0.1 psec,
  then time to refold (t) 1087 sec

• directed pathways of folding must exists

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Framework model
Formation of elements of 2-stru.
Assembly of 2-stru.
Folded con.
Unfolded state
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GCN4 leucine zipper
gabcdefgabcdefgabcdefgabcdefgabcd STHMKQLED
KVEELLSKNYHLENEVARLKKLVGER
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CD spectra of GCN4 leucine zipper in the presence
of different concentrations of SDS
4 M GuHCl
SDS
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Changes of ellipticity at 222 nm in the presence
of different concentrations of SDS
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Native gel electrophoresis of leucine zipper
treated with SDS of different concentrations
Lane 1 was the native leucine zipper peptide
(control) lanes 2- 6 were samples treated with
0.1, 0.2, 0.3, 0.6, and 1.0 mM SDS
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Energy surfaces to visualize protein folding
pathways
a more realistic energy landscape
A
the protein is funneled towards a native state
many pathways are possible
some lead straight downhill
others may lead to energy minima that delay
proper folding
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Changes of fluorescence emission spectra of Tg
denatured in various concentrations of GuHCl
Thyroglobulin
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ANS binding characteristics of Tg in various
GuHCl concentrations
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??? (M) ?? ?? ??
??? (M) OPTA OPTA ???? ?? ??
??? (M) k1 k2 ???? k1 k2
0.3 0.38 0.049 0.015
0.5 1.18 0.11 0.0038 3.6 0.003
1.0 2.9 0.04 4.3
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• ???

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Proteinprotein interface design
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erythropoietin
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(No Transcript)
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EPO-EPOR
ERPH1-EPOR
LiuS,LiuSY,ZhuXL, LiangHH,CaoAN,ChangZJandLaiLH.
Nonnaturalprotein-proteininteraction-pairdesignby
keyresiduesgrafting. PNAS,2007,104,5330
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?????A?1-40????? ????,????????,2000,16
FT - IR spectra of A?1 - 40 in PBS(pH7. 4) for
30min
FT - IR spectra of A?1 - 40 in PBS(pH7. 4) for 7
days
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FT- IR spectra of A?1 - 40 in PBS(pH7. 4) with
TA9901 for 7 days (percent ratio A?1 40
TA9901 11)
FT - IR spectra of A?1 - 40 in PBS(pH7. 4) for 7
days
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? ? ? ? ? ? ? ? ? ?????????
A1635/A1652 A1625/A1652 A1645/A1652 A1662/A1652 A1682/A1652
benign 0.98 0.65 0.64 0.49 0.17
malignant 0.43 0.23 0.56 0.37 0.09
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HSP ????

• ???
• (??)

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????molecular chaperones
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Misfolding Protein Conformational Disorders
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?????????????
Mad cow
TSE
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Alzheimers D. Amyloid ? Protein
Tau protein
Conformational Brains Disorders
Parkinson D. a-synuclein
Huntington D. Glutamine-repeat
Protein Conforma- tional Disorders (PCD)
Prion D. Prion protein
Sickle cell anaemia
Haemoglobin
Familial visceral Amyloidosis
Lysozyme .
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Human Prion Diseases

• Sporadic form
• Creutzfeldt-Jakob disease (CJD)
• Familial (inherited) form
• Familial CJD
• Fatal familial insomnia
• Gerstmann-Straussler-Scheinker syndrome
• Acquired (transmitted) form
• Iatrogenic CJD
• Kuru
• New Variant CJD (related to Mad Cow Disease)

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Animal Prion Diseases

• Scrapie
• Sheep and goat
• Bovine spongiform encephalopathy (Mad Cow
  Disease)
• Cattle
• Feline spongiform encephalopathy
• Cat (domestic cats, cheetahs, pumas)
• Transmissible mink encephalopathy
• Mink
• Chronic wasting disease
• Mule deer, elk

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???(Prion)??????
??????? ???????????????????????, ????????,??????P
rP??,????? ???
???? ?????????????
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Prion Protein Gene (PRNP)
---Located on chromosome 20 in humans, chromosome
2 in mouse ---Encodes a glycoprotein with two
sites for N-linked oligosaccharites and a
C-terminal GPI anchor ---High expression in
brain. Lower expression in peripheral
tissues ---10-15 of all cases are familial.
About 20 mutations are linked to familial disease.
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The Nobel Prize in Physiology or Medicine
1976for their discoveries concerning new
mechanisms for the origin and dissemination of
infectious diseases
Baruch S. Blumberg
D. Carleton Gajdusek
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Stanley B. PrusinerThe Nobel Prize in Physiology
or Medicine 1997for his discovery of Prions - a
new biological principle of infection
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1. Genetics
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2. Protein
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Conformational transition from alpha-helix rich
to beta-sheet rich
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PrPsc
PrP27-30
PrPc
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References

• Roger H.Pain, Mechanisms of Protein Folding
• Bengt Nölting, Proein Folding Kinetics
  Biophysical Methods
• Leninger, Principles of Biochemistry,Worth
  Publishing,
• Mathews and Van Holde, Biochemistry, Benjamin
  Cummings

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