Fig. 8. Structural conservation of SiaPQM around the allosteric pocket that forms the VHH_VcP #2 epitope.

a Model of the tripartite SiaPQM complex from Vibrio cholerae. The model was built up from AlphaFold2 predictions and experimental structures. The binding area of VHH_VcP #2 is indicated and labelled. The Q (teal) and M(red) transmembrane domains are depicted as cartoon model and the P-domain is shown as surface representation. On the right-hand-side, a magnification of the region of interest is shown and the highlighted amino acid residues are labeled. b Same as (a) but for the tripartite SiaPQM complex from Haemophilus influenzae. c Sequence logo to visualize the hydrophobic loop of the Q-domain that is conserved among sialic acid TRAP transporters and includes the conserved Phe residue 118 (111 in HiSiaQ). This image was created with WebLogo⁴⁷ and was adapted from Peter et al.²¹ (http://creativecommons.org/licenses/by/4.0/).