Fig. 2.

Binding of sialic acid oligosaccharides to P110. a Schematic representation of the disposition of P110 with respect to the mycoplasma membrane (same color code as in Fig. 1). The predicted transmembrane helix follows in sequence to the C-domain, which accordingly is expected to be close to the cell membrane. The overall structure of P110 can be sketched as a capital letter P with the sialic binding site (indicated in the figure with a rectangle) located in the crown, away from the cell membrane. Detail of the binding to P110 of sialic acid oligosaccharides b 3SL and c 6SL. Left panels show the electron density corresponding to oligosaccharides in a sigma weighted (Fo–Fc) omit map at two sigma. The binding site and the binding interactions with P110 for both oligosaccharides are very similar, but not identical