Local Protein Unfolding and Pathogenesis of PolyglutamineExpansion Disease

About This Presentation

Title:

Local Protein Unfolding and Pathogenesis of PolyglutamineExpansion Disease

Description:

... are characterized by high net charge and low hydrophobicity. ... ProtScale is used to calculate hydrophobicity. ProtParam. Global protein folding prediction ... – PowerPoint PPT presentation

Number of Views:115

Avg rating:3.0/5.0

Slides: 23

Provided by: gelY1

Category:

more less

Transcript and Presenter's Notes

Title: Local Protein Unfolding and Pathogenesis of PolyglutamineExpansion Disease

1
Local Protein Unfolding and Pathogenesis of
Polyglutamine-Expansion Disease

Yu Wai Chen
Centre for Protein Engineering and Cambridge
University Chemical Laboratory, Cambridge, United
Kingdom
Proteins 20035168-73
speaker S.C.Fu
24/04/03

2
What is Polyglutamine-Expansion Disease?

Polyglutamine-Expansion
Abnormal lengthening of polyglutamine (polyQ)
repeat sequence inside the protein.
Inherited neurodegenerative disease such as
Huntingtons disease and spinocerebellar ataxia
(SCA) have been shown to be caused by polyQ
repeat.

3
Elongation of CAG repeat

Petruska et. al. 1998

4
These Inherited neurodegenerative diseases

Causing misfolding and aggregation of disease
proteins.
Expansion of Glutamine repeat gt 3540 residues
confers on disease proteins a toxic gain of
function that cause tissue-specific neuronal
death.
Progress via a similar pathogenic mechanism.
Apart from polyQ repeat, these proteins and their
genes have nothing in common.

5
(No Transcript)
6
Hypothesis

PolyQ disease proteins may share a common feature
of being natively unfolded and are thus
susceptible to misfolding and aggregation.

7
Unfolded
8

Proteins that are natively unfolded are
characterized by high net charge and low
hydrophobicity.
They found that for a given protein with a mean
net charge of ltRgt, a boundary value exists for
its mean hydrophobicity, ltHgt, below which the
protein is likely to be natively unfolded. This
empirical relationship is expressed as

9
(No Transcript)
10
Materials and Methods

Dataset (from the SWISS-PROT database)
Huntingtons disease protein (or huntingtin, Htt,
P42858)
androgen receptor (AR, P10275)
atrophin-1 (Atf1,also known as dentatorubral-palli
doluysian atrophy protein,P54259)
spinocerebellar ataxin-1 (Atx1, P54253),
ataxin-2 (Atx2, Q99700)
ataxin-3 (Atx3, also known as Machado-Joseph
disease protein, MJD, P54252)
ataxin-6(Atx6, O00555)
ataxin-7 (Atx7, O15265)
sperm whale myoglobin (Mb, P02185)
The TATA-box-binding protein (TBP or TF2D,
referred to as Atx17 here, P20226)

11
Materials and Methods

Using ProtParam program from ExPASy for net
calculation.
ProtScale is used to calculate hydrophobicity.

12
ProtParam
13
Global protein folding prediction

blue dots (excluding polyQ)
red dots (including the polyQ)

14
Result of global and local protein folding
prediction
15
Local protein folding prediction

blue dots (excluding polyQ)
red dots (including the polyQ)

16
Compared with experimental observation

An artificial system to study the structural
consequences of introducing repeats of 12, 28,
35, and 50 glutamines into sperm whale myoglobin
(Mb).
Mb-12
Mb-28
Mb-35
Mb-50

17
Compared with experimental observation
18
Compared with experimental observation

The studies of secondary structures of several
fusion constructs of Atx3 using circular
dichorism (CD) spectroscopy
Atx3 and maltose-binding protein fusions
(MBP-Atx3-Q27 and MBPAtx3-Q78)
hexahistidine-tagged ataxin-3 (H6-Atx3-Q27)

19
Circular dichorism

Circular dichroism is the difference in
absorption between left and right handed circular
polarized light.
is used to gain information about the secondary
structure of proteins and polypeptides in
solution.
very sensitive to the secondary structure of
polypeptides and proteins.