Figure 6.

Crystal structure of the reduced CcScsC C2S protomer. (a) Model of the CcScsC C2S protomer in a combination of cartoon and surface representations. CcScsC C2S is composed of a long N-terminal α-helix (N-term) and a globular domain. The structure is rotated 90° along its long axis to facilitate visualization of the whole protein, including its C-terminal α-helix (C-term). The scale box provides a reference for the size of the protein. The active site is highlighted by a pink circle. (b) Secondary-structure elements of CcScsC C2S. The protein is comprised of ten α-helices: three in the N-terminal tail and seven in the globular domain. Residues His22 and Pro23, which are part of the bend in the N-terminal domain, are shown as sticks and highlighted with a red arrow between helices α1 and α2. The globular domain supports a typical thioredoxin fold, coloured green, with the two catalytic cysteines represented as pink sticks facing Thr191–cis-Pro192, which is also shown in pink and highlighted with a red arrow.