Multiple alignment (A) and structural modelling (B) of TFIIS domains. The domain sequences were predicted by the Pfam HMM programme and aligned using the CLUSTALW programme. The 3-dimensional structures of the domains were generated using the 3D-jigsaw comparative modelling programme and the VAST search programme and visualised by the Cn3D programme (Version 4.1). Identical (*) and similar (:, .) residues are shown below the alignment. Cysteines (C1–4) involved in zinc (Zn) binding are indicated by arrows in the alignment and the 3D structures. Amino acid position of the domain position is listed in Table 2. Predicted α-helices (green), β-strands (purple or dark blue) and loops (light blue) are marked in both the alignment and the 3D structures respectively.