Fig. 3. L2 and S2 structures of the PreQ₁-free, PreQ₁-bound, and the compounds 4 and 8-bound forms.

A Superimposed structures of the 4-bound and PreQ₁-free forms (left), the 4-bound and PreQ₁-bound forms (second left), the 8-bound and PreQ₁-free forms (second right), and the 8-bound and PreQ₁-bound forms (right). L2, A32, and G33 in S2 are color-coded as indicated. PreQ₁ and compounds 4 and 8 are in yellow. B Structural comparison highlighting the conformational differences of A32 and G33 in S2, with the same color codes as (A).