Fig. 5.

Comparison of protein/peptide binding modes in the BsTrxA C32S dimer and other thioredoxin peptide and protein complexes. (a) BsTrxA was superimposed on the thioredoxin from other complexes using PyMOL.³⁵ The superimposed structures, the surface of chain A of BsTrxA, and the peptide or protein chain of the bound molecule are shown. The disulfides and large hydrophobic residues that contribute to binding are also shown. The N- and C-termini of the bound peptides and proteins are indicated with the letters N and C. The proteins shown in (a) are as follows: the BsTrxA dimer with residues 26–38 of chain B shown as cartoons and the side chains of Trp28 and Cys29 shown as sticks (this study; dark blue); the NMR structures of human thioredoxin complexed with substrate peptides from Ref-1 (1CQH; red) or NF-κB (1MDJ; green) with the side chains of residues Cys65 and Tyr67 of the Ref-1 peptide and of residues Trp60 and Cys62 of the NF-κB peptide; the NMR structure of the B. subtilis TrxA and ArsC (2IPT; purple) with residues Cys89 and Met91; and the X-ray structure of the complex between barley thioredoxin and the α-amylase serine proteinase inhibitor (2IWT; orange) with residues Trp147 and Cys148. (b) Comparison of the BsTrxA (dark blue) dimer interface with the binding of thioredoxin reductase by E. coli thioredoxin (1F6M; yellow) and the X-ray structures of the complexes between spinach chloroplast thioredoxins Trx-f and Trx-m and ferrodoxin–thioredoxin reductase (2PU9 and 2PUK; in cyan and magenta, respectively). Trp28 is shown for the TrxA structure (dark blue), and the E. coli thioredoxin reductase structure shows Phe142 (yellow).