Fig. 3.

The N-terminal domain and the “rider” domain of K1 lyase. a Superimposition in the monomer of the N-terminal domain of the K1 lyase (orange) and the human collagen XVIII trimerization domain (cyan) [35]. b Comparison in the trimer of the two structures described in (a). The N-terminal and C-terminal end in a subunit of both structures are indicated. c The “rider” domain, a strikingly protruding structure at the central β-helix, displaying a β-barrel-like fold. d Superimposition of the “rider” domain (yellow) and the I-domain of bacteriophage P22 coat protein (purple) [36]. The unstructured loops in both structures are colored gray. e Interaction of the “rider” domain (green) with the β-helix of a neighboring subunit (magenta). f Comparison of thermal stabilities of wild-type (black) and mutant (red) K1 lyase, as evaluated by circular dichroism spectroscopy