# Synthetic protein design: construction of a four-stranded $\beta$-sheet structure and evaluation of its integrity in methanol-water systems

Das, C and Nayak, V and Balaram, P and Raghothama, S (2000) Synthetic protein design: construction of a four-stranded $\beta$-sheet structure and evaluation of its integrity in methanol-water systems. In: Journal of Peptide Research, 56 (5). pp. 307-317.

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## Abstract

The characterization of a four-stranded $\beta$-sheet structure in a designed 26-residue peptide Beta-4 is described. The sequence of Beta-4 (Arg-Gly-Thr-Ile-$Lys-^D$pro-Gly-Ile-Thr-Phe-$Ala-^D$Pro-Ala-Thr-Val-Leu-Phe-Ala-$Val-^D$ Pro-Gly-Lys-Thr-Leu-Tyr-Arg) was chosen such that three strategically positioned $^DPro$-Xxx segments nucleate type II′$\beta$-turns, which facilitate hairpin extension. A four-stranded $\beta$-sheet structure is determined in methanol from 500 MHz $^1 H \hspace{1mm} NMR$ data using a total of 100 observed NOEs, 11 dihedral restraints obtained from vicinal $J_{C\alpha H-NH}$ values and 10 hydrogen bonding constraints obtained from H/D exchange data. The observed NOEs provide strong evidence for a stable four-stranded sheet and a nonpolar cluster involving $Ile^8$, $Phe^{10}$, $Val^{15}$ and $Phe^{17}$. Circular dichroism studies in water-methanol mixtures provide evidence for melting of the $\beta$-sheet structure at high water concentrations. NMR analysis establishes that the four-stranded sheet in Beta-4 is appreciably populated in 50% (v/v) aqueous methanol. In water, the peptide structure is disorganized, although the three $\beta$-turn nuclei appear to be maintained.

Item Type: Journal Article Copyright of this article belongs to Blackwell. Protein design;Designed b-sheet motif;Synthetic peptide;Conformational analysis;NMR Division of Biological Sciences > Molecular Biophysics Unit 09 Oct 2007 19 Sep 2010 04:40 http://eprints.iisc.ernet.in/id/eprint/12179