Characterization of (Boc-Cys/Sec-NHMe)2 and (Boc-Cys/Sec-OMe)2: Evidence of local conformational difference between disulfide and diselenide

Dolle, A and Reddy, KKA and Gunaga, SS and Krishnamurthy, K and Senapati, DK and Rana, A and Sindogi, K and Biswal, HS and Raghothama, S and Gowd, KH (2020) Characterization of (Boc-Cys/Sec-NHMe)2 and (Boc-Cys/Sec-OMe)2: Evidence of local conformational difference between disulfide and diselenide. In: Journal of Peptide Science, 26 (4-5).

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Abstract

Conformations of disulfide and diselenide were compared in (Boc-Cys/Sec-NHMe)2 and (Boc-Cys/Sec-OMe)2 using X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, density functional theory (DFT), and circular dichroism (CD) spectroscopy. Conformations of disulfide/diselenide in polypeptides are defined based on the sign of side chain torsion angle �3 (�CH2�S/Se�S/Se�CH2�); negative indicates left-handed and positive indicates right-handed orientation. In the crystals of (Boc-Cys-OMe)2 and (Boc-Sec-OMe)2, the disulfide exhibits a left-handed and the diselenide a right-handed orientation. Characterization of cystine and selenocystine derivatives in solution using 1H-NMR, natural abundant 77Se NMR, 2D-ROESY, and chemical shift analysis coupled to DMSO titration has indicated the symmetrical nature and antiparallel orientation of Cys/Sec residues about the disulfide/diselenide bridges. Structural calculations of cystine and selenocystine derivatives using DFT further support the antiparallel orientation of Cys/Sec residues about disulfide/diselenide. The far-ultraviolet (UV) region CD spectra of cystine and selenocystine derivatives have exhibited the negative Cotton effect (CE) for disulfide and positive for diselenide confirming the difference in the conformational preference of disulfide and diselenide. In the previously reported polymorphic structure of (Boc-Sec-OMe)2, the diselenide has right-handed orientation. In the X-ray structures of disulfide and diselenide analogues of Escherichia coli protein encoded by curli specific gene C (CgsC) retrieved from Protein Databank (PDB), disulfide has left-handed and the diselenide right-handed orientation. The current report provides the evidence for the local conformational difference between a disulfide and a diselenide group under unconstrained conditions, which may be useful for the rational replacement of disulfide by diselenide in polypeptide chains.

Item Type:	Journal Article
Publication:	Journal of Peptide Science
Publisher:	John Wiley and Sons Ltd
Additional Information:	The copyright of this article belongs to John Wiley and Sons Ltd
Department/Centre:	Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility) Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	25 Jun 2020 10:06
Last Modified:	25 Jun 2020 10:06
URI:	http://eprints.iisc.ac.in/id/eprint/64829

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