Nuclear magnetic resonance studies of recombinant Escherichia coli glutaredoxin: Sequence‐specific assignments and secondary structure determination of the oxidized form

Escherichia coli glutaredoxin (85 amino acid residues, M_r= 9100), the glutathione‐dependent hydrogen donor for ribonucleotide reductase, was purified from an inducible λpl expression system both with a natural isotope content and with uniform ¹⁵N labelling. This material was used for obtaining sequence‐specific ¹H magnetic resonance assignments and the identification of regular secondary structures in the oxidized form of the protein, which contains the redox‐active disulfide . Oxidized glutaredoxin contains a four‐stranded β‐sheet, with the peripheral strand 32–37 arranged parallel to the strand 2–7, which further combines with the two additional strands 61–64 and 67–69 in an antiparallel fashion. The protein further contains three helices extending approximately from residues 13–28, 45–54 and 72–84.