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N‐1 and N‐2 positional effects in the propagation of 3 10 ‐type fold in the helical model peptide Boc– ( D )Glu– Pro– Ala– Lys– Ala– Leu– Ala– OMe
Author(s) -
Beri S.,
Srivastava Sudha,
Dhanasekaran M.,
Phadke Ratna S.,
Durani S.
Publication year - 2000
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(200004)38:4<257::aid-mrc627>3.0.co;2-w
Subject(s) - chemistry , helix (gastropod) , peptide , stereochemistry , crystallography , biochemistry , ecology , snail , biology
The N‐1 (Ala 2 ) and N‐2 (Gly 3 ) positional amino acids in the type II ′ turn templated 3 10 helix Boc–( D ) Glu 1 – Ala 2 –Gly 3 –Lys 4 –NHMe ( 1 ) and Boc–( D )Glu 1 –Ala 2 –Gly 3 –Lys 4 –Ala 5 –Leu 6 –OMe ( 3 ) are substituted with Pro 2 and Ala 3 to obtain its variants Boc– ( D )Glu 1 –Pro 2 –Ala 3 –Lys 4 –NHMe( 2 ) and Boc–( D ) Glu 1 –Pro 2 –Ala 3 –Lys 4 –Ala 5 –Leu 6 –Ala 7 –OMe ( 4 ). According to NMR evidence, the resultant peptide ( 4 ) is also a 3 10 ‐type helix endlocked by Boc– ( D )Glu 1 , with a stronger Lys→ Glu salt bridge but a comparatively weaker helical domain, more susceptible to solvent‐mediated disordering. The relatively constrained residues of higher N cap and internal positional helix propensities are thus shown actually to weaken the helical domain in our model, because its helix‐templating segment distorts and thus its template‐assisted propagation as a 3 10 helix is compromised. The dependence of geometry and stability of an ordered helical structure on effects in its folding initiation and template‐assisted propagation are thus shown to be captured in a helical model peptide of unusual structural simplicity. Copyright © 2000 John Wiley & Sons, Ltd.