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Designed Peptides with Homochiral and Heterochiral Diproline Templates as Conformational Constraints

Chatterjee, Bhaswati and Saha, Indranil and Raghothama, Srinivasarao and Aravinda, Subrayashastry and Rai, Rajkishor and Shamala, Narayanaswamy and Balaram, Padmanabhan (2008) Designed Peptides with Homochiral and Heterochiral Diproline Templates as Conformational Constraints. In: Chemistry - A European Journal, 14 (20). pp. 6192-6204.

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Diproline segments have been advanced as templates for nucleation of folded structure in designed peptides. The conformational space available to homochiral and heterochiral diproline segments has been probed by crystallographic and NMR studies on model peptides containing L-Pro-L-Pro and D-Pro-L-Pro units. Four distinct classes of model peptides have been investigated: a)isolated D-Pro-L-Pro segments which form type II' \beta -turn; b) D-Pro-L-Pro-L-Xxx sequences which form type II'-I $(\beta_{II'-I}$, consecutive \beta -turns) turns; c) D-Pro-L-Pro-D-Xxx sequences; d) L-Pro-L-Pro-L-Xxx sequences. A total of 17 peptide crystal structures containing diproline segments are reported. Peptides of the type Piv-D-Pro-L-Pro-L-Xxx-NHMe are conformationally homogeneous, adopting consecutive \beta-turn conformations. Peptides in the series Piv-D-Pro-L-Pro-D-Xxx-NHMe and Piv-L-Pro-L-Pro-L-Xxx-NHMe, display a heterogeneity of structures in crystals. A type VIa \beta -turn conformation is characterized in Piv-L-Pro-L-Pro-L-Phe-OMe (18), while an example of a 5\rightarrow 1 hydrogen bonded \alpha-turn is observed in crystals of Piv-D-Pro-L-Pro-D-Ala-NHMe (11). An analysis of pyrrolidine conformations suggests a preferred proline puckering geometry is favored only in the case of heterochiral diproline segments. Solution NMR studies, reveal a strong conformational influence of the C-terminal Xxx residues on the structures of diproline segments. In L-Pro-L-Pro-L-Xxx sequences, the Xxx residues strongly determine the population of Pro-Pro cis conformers, with an overwhelming population of the trans form in L-Xxx = L-Ala (19).

Item Type: Journal Article
Publication: Chemistry - A European Journal
Publisher: John Wiley & Sons
Additional Information: Copyright of this article belongs to John Wiley & Sons.
Keywords: Beta turns;conformation;analysis;peptide folding;peptides.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility)
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 19 Aug 2008
Last Modified: 19 Sep 2010 04:49
URI: http://eprints.iisc.ac.in/id/eprint/15581

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