homology modeling seminar produced by hanka venselaar
Post on 22-Dec-2015
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TRANSCRIPT
Homology modeling
# residues
% id
entit
y
*
* Actually, modelling is possible here, but we cannot get an alignment…
Yes we can
Homology modeling in short…Prediction of structure based upon a highly similar structure
Add sidechains, Molecular Dynamics simulation on model
Unknown structure
NSDSECPLSHDG
NSDSECPLSHDG
|| || | ||
NSYPGCPSSYDG
Alignment of model and template sequence
Known structure
Known structure Back bone copiedCopy backbone and conserved residues
Model!
1: Template recognition and initial alignment
• BLAST your sequence against PDB
• Best hit normally template
2: Alignment correction
• Functional residues conserved• Use multiple sequence alignments• Deletions shift gaps
CPISRTGASIFRCW CPISRTGASIFRCWCPISRTA---FRCW CPISRT---AFRCW
CPISRTAAS-FRCWCPISRTG-SMFRCWCPISRTA--TFRCWCPISRTAASHFRCWCPISRTGASIFRCW CPISRTA---FRCW
Both are possible
Multipe sequence alignment
Correct alignment
Sequence with known structure
Your sequence
2: Alignment correction
• Core residues conserved• Use multiple sequence alignments• Deletions in your sequence shift gaps
Known structure FDICRLPGSAEAV
Model FNVCRMP---EAI
Model FNVCR---MPEAI
S
G
P
L
A
E
R
C
I V
C
R
M
P
EV
C
R M
P
E
Correct alignment
F-D--A-V
3: Backbone generation
• Making the model….• Copy backbone of template to model• Make deletions as discussed• (Keep conserved residues)
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
4: Loop modeling
Known structure GVCMYIEA---LDKYACNC
Your sequence GECFMVKDLSNPSRYLCKC
Loop library,
try different options
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
5: Sidechain modeling
5: Side-chain modeling
• Several options
• Libraries of preferred rotamers based upon backbone conformation
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
5: Sidechain modeling
6: Model optimization
6: Model optimization
• Molecular dynamics simulation• Remove big errors
• Structure moves to lowest energy conformation*
* Which has nothing to do with the real coordinates...
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
5: Sidechain modeling
6: Model optimization
7: Model validation
7: Model Validation
• Second opinion by PDBreport /WHAT IF
• Errors in active site? new alignment/ template
• No errors? Model!
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
5: Sidechain modeling
6: Model optimization
7: Model validation
8: Iteration
8: Iteration
8: Iteration
8: Iteration
Model!
1: Template recognition and initial alignment
2: Alignment correction
3: Backbone generation
4: Loop modeling
5: Sidechain modeling
6: Model optimization
7: Model validation
8: Iteration
8: Iteration
8: Iteration
8: Iteration