Differences in the size of the CSP binding pockets can reflect ligand differences.

<p>The N-terminus is indicated. The 34 binding-residues are shown as sticks. Certain binding-residues of interest are indicated in each CSP. (A) Residues within 5 Å of the ligands in the ligand-bound <i>M. brassicae</i> structure (PDB-ID: 1N8V) were considered as binding-residues. The bromo-dodecanol ligands are visualized inside the pocket. (B) The model of CSP1 shown here represents a binding pocket of a non-ligand bound typical CSP protein. (C) The binding pocket of CSP5 is likely enlarged due to the lack of helix 6 and mutations that reduce the size of the binding-residues (A44, Q54, A58 V67 and V36). (D) The binding pocket of CSP7 model is crowded by large binding-residues. For example, F50 and W28 are larger than the corresponding amino acid residues in other, typical CSPs.</p

Size distribution of the binding pocket residues.

<p>Size distribution of the binding pocket residues.</p

Ant-specific CSPs share similarities with CSP7, and positive selection in them is concentrated on the surface.

<p>(A) Left, molecular model of CSP7 shows a “crown” of charged residues (circled). The crown is formed by the positive loop between helices 3 and 4, and by the negative charge between helices 5 and 6. The ant-specific proteins (right) all have this crown. Positively charged residues (K, R) are shown in blue and negatively charged (D, E) in red. (B) The ten residues under positive selection (shown as sticks on the peptide backbone) mostly map on the surface. L87 and L91 are the only binding residues under positive selection. K58 and A66 are located near the “crown” and have various combinations of positive charge and hydrophobicity in the ant-specific CSPs. The N and C termini are indicated.</p

Surface charge variation in orthologous ant CSPs between the seven ant species.

<p>Surface charge variation in orthologous ant CSPs between the seven ant species.</p

Groups of ant CSPs based on their phylogeny and structural models.

<p>All ants share seven orthologous CSPs (CSP1-7; the uppermost row of models), of which CSP7 or a protein similar to that has given rise to the ant-specific expansions (representative proteins on the middle row). The largest currently known ant-expansion is found in <i>S. invicta</i> (the lowest row). In the orthologs, CSP1-4 can be grouped together based on their evenly speckled surface charges and similarities in their binding pocket (“Typical CSPs”; green). CSP5 (grey) is conserved across arthropods, and is one of the oldest CSPs. It differs from the other orthologs by having five instead of six helices, a reduced charge on the surface and by changes to its binding pocket. CSP6 and CSP7 are grouped together (purple) due to mutations in their binding pocket that are likely to reduce the size of the pocket cavity. Examples of the ant-specific CSP expansion are shown; <i>Atta cephalotes</i> CSP8, <i>Pogonomyrmex barbatus</i> CSP10, <i>Camponotus floridanus</i> CSP11, <i>Acromyrmex echinatior</i> CSP14 and <i>Solenopsis invicta</i> CSP17. In the models, negatively charged amino acids (E, D) are shown in red and positively charged amino acids (K, R) in blue. C-termini are marked by an arrow. The <i>S. invicta</i> expansion proteins, together with CSP5, are one helix shorter than the other CSPs in their C-terminus, which is depicted by the altered location of the arrow in these models.</p

Chemical characteristics of the ten amino acid residues under positive selection.

<p>Chemical characteristics of the ten amino acid residues under positive selection.</p

Morandin et al. FexsVgs alignment

This file contains alignment generated via ClustalX of Vitellogenin and Vitellogenin-like sequences of Formica exsecta

Morandin et al. Vg sequences

This file contains Vitellogenin and Vitellogenin-like sequences (amino acid and predicted protein) used for the phylogenetic tree (Figure 1), annotated in insect species for Morandin et al. 2014