Sequence conservation within the actin-binding region of the β-subunits. The sequence logos are based on 299 β-subunit sequences and illustrate the sequence conservation within the multiple sequence alignment of the β-subunits. Two regions known to be important for actin-binding are shown (For the representation of the entire β-subunits see Additional file3). For better orientation, the sequences of three representative β-subunits are shown: chicken Cap2 of which all previous crystal structures have been obtained, the yeast Cap2 as one of the targets of mutagenesis experiments, and Dictyostelium Cap32 whose structure is presented here. Secondary structural elements, important residues indicating various interactions, and taxa/species with elongated loops are denoted as in Figure 4 (The full-length multiple sequence alignment of the β-subunits is available as Additional File4). Loops, which exist only in single species, have been removed to shorten the alignment by the number of residues as indicated. Numbering below the logos refers to positions in the multiple sequence alignment.