An intraresidue H-bonding motif in selenocysteine and cysteine, revealed by gas phase laser spectroscopy and quantum chemistry calculations - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Physical Chemistry Chemical Physics Année : 2020

An intraresidue H-bonding motif in selenocysteine and cysteine, revealed by gas phase laser spectroscopy and quantum chemistry calculations

Résumé

Models of protein chains containing a seleno-cysteine (Sec) residue have been investigated by gas phase laser spectroscopy in order to document the effect of the H-bonding properties of the SeH group in the folding of the Sec side chain, by comparison with recent data on Ser- and Cys-containing sequences. Experimental data, complemented by quantum chemistry calculations and natural bonding orbital (NBO) analyses, are interpreted in terms of the formation of a so-called 5g intra-residue motif, which bridges the acceptor chalcogen atom of the side chain to the NH bond of the same residue. This local structure, in which the O/S/Se atom is close to the plane of the N-terminal side amide, is constrained by local backbone-side chain hyperconjugation effects involving the S and Se atoms. Theoretical investigations of the Cys/Sec side chain show that (i) this 5g motif is an intrinsic feature of these residues, (ii) the corresponding H-bond is strongly non-linear and intrinsically weak, (iii) but enhanced by g- and b-turn secondary structures, which promote a more favorable 5g H-bonding approach and distance. The resulting H-bonds are slightly stronger in selenocysteine than in cysteine, but nearly inexistent in serine, whose side chain in contrast behaves as a H-bonding donor. The modest spectral shifts of the Cys/Sec NH stretches measured experimentally reflect the moderate strength of the 5g H-bonding, in agreement with the correlation obtained with a NBO-based H-bond strength indicator. The evolution along the Ser, Cys and Sec series emphasizes the compromise between the several factors that control the H-bonding in a hyperconjugation-constrained geometry, among them the chalcogen van der Waals and covalent radii. It also illustrates the 5g H-bond enhancements with the Sec and Cys residues favoured by the constraints imposed by the g- and b-turn structures of the peptide chain.
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hal-03443065 , version 1 (15-02-2024)

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Gildas Goldsztejn, Venkateswara Rao Mundlapati, Jérémy Donon, Benjamin Tardivel, Eric Gloaguen, et al.. An intraresidue H-bonding motif in selenocysteine and cysteine, revealed by gas phase laser spectroscopy and quantum chemistry calculations. Physical Chemistry Chemical Physics, 2020, 22 (36), pp.20409-20420. ⟨10.1039/D0CP02825H⟩. ⟨hal-03443065⟩
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