A, In the crystal structure (PDB ID 4CW9), the EhTrxC34S mutant (shown in ribbon) is cross-linked via formation of the disulfide bond (in stick representation) formed between the C31 thiol groups. B, In the EhTrxC34S mutant, N-terminus of the α-helix 2 accommodating catalytic dithiol motif adopts α-helical structure in chain B which unwinds in chain A. In B, both chains are shown in the same orientation derived from superimposition of their structures.