(a) Alignment of Arabidopsis Whirly ssDNA-binding sites. Proteins are shown in cartoon representation and residues equivalent to those of potato WHY2 (PDB entry 3n1i) that contact ssDNA are shown in stick representation with C atoms in grey. Those of WHY1, WHY2 and WHY3 are shown in cyan, magenta and green, respectively. The potato WHY2 nomenclature was used for clarity. The ssDNA is shown in stick representation with its C atoms in yellow. (b) Close-up of residues Trp100 and Trp110. The representation is similar to that in (a).