Selenoproteins are a specialized group of enzymes that contain the rare amino acid selenocysteine (Sec). The majority of selenoproteins pair the reactive Sec with a Cys, positioned up to two amino acids away. It is predicted that the nature of the residues forming this motif and the size of the resulting ring control Sec's reactivity. We demonstrate that it is possible to probe Sec's local environment and flexibility in these redox motifs using 77Se NMR spectroscopy. To that end we have developed a generally applicable 77Se isotopic enrichment method for heterologous proteins expressed in Escherichia coli. Consequently, we are able to record the 77Se chemical shifts and relaxation properties of reduced and oxidized selenoproteins. We show that the Cys-Sec redox motif is inherently more rigid then the Cys-Gly-Ala-Sec motif and that the residues immediate to the redox motif also govern flexibility.

<sup>77</sup>Se NMR of selenoproteins' redox motifs revels differences in inherit flexibility

244th National Meeting (2012)

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77Se NMR of selenoproteins' redox motifs revels differences in inherit flexibility

⁷⁷Se NMR of selenoproteins' redox motifs revels differences in inherit flexibility