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Conformational features of a hexapeptide model Ac-TGAAKA-NH2 corresponding to a hydrated α helical segment from Glyceraldehyde 3-phosphate dehydrogenase role of turns in helix folding

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Title Conformational features of a hexapeptide model Ac-TGAAKA-NH2 corresponding to a hydrated α helical segment from Glyceraldehyde 3-phosphate dehydrogenase role of turns in helix folding
 
Creator Sasidhar, Y U
Ramakrishna, V
 
Description 34-44
Recent analysis of α helices in protein crystal
structures, available in literature, revealed hydrated α
helical segments in which, water molecule breaks open helix 5 →1
I hydrogen bond by inserting itself, hydrogen bonds to both C=O and NH groups of
helix hydrogen bond without disrupting the helix hydrogen bond, and hydrogen
bonds to either C=O or NH of helix hydrogen bond. These hydrated segments
display a variety of turn conformations and are thought to be 'folding intermediates'  trapped  during folding-unfolding
of α  helices.
A role for reverse turns is implicated  in  the
folding of α helices. We considered a hexapeptide model Ac-1TGAAKA6-NH2. from
glyceraldehyde 3-phosphate dehydrogenase ,corresponding to a hydrated helical segment to
assess its role in helix folding.  The
sequence is a site for two 'folding intermediates'. The conformational features
of the model peptide have been investigated by 1H 2D
NMR techniques and quantum mechanical perturbative configuration interaction
over localized orbitals (PCILO) method. Theoretical modeling largely correlates
with experimental observations. Based upon the amide proton temperature
coefficients, the observed  dαn(i,
i+ 1), dαn(i, i+2), dnn(i, i+ 1 ), dβn(i, i+ 1) NOEs
and the results from theoretical modeling, we conclude
that the residues of the peptide sample α
helical and neck regions of the Ramachandran φ,Ψ map with reduced conformational
entropy
and there is a potential for turn conformations at N and C terminal
ends of the peptide. The role of reduced conformational entropy and turn
potential in helix formation have been discussed. We conclude
that the peptide sequence can serve as a 'folding intermediate' in the helix
folding of glyceraldehyde 3-phosphate dehydrogenase.
 
Date 2012-12-28T11:31:16Z
2012-12-28T11:31:16Z
2000-02
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/15369
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.37(1) [February 2000]