Figure 5.

FusA Structural Determinants for Carbohydrate Binding Are Involved in FOS Import

(A) Growth curves of S. pneumoniae on defined medium containing nystose as a sole carbon source. Endogenous FusA was mutated as described for each panel. An optical density at 600 nm (OD₆₀₀) for wild-type and every mutant was measured every 20 min for 96 hr, showing that most of the mutants have impaired growth on nystose.

(B) Schematic representation of the FusA-FOS-binding site, highlighting the residues involved in FOS binding and import: dotted lines indicate hydrogen bonds or polar interactions, while the gray ring represents the stacking interaction of Trp314 on F₂. Mutation of these amino acids affect strongly (red), weakly (yellow), or do not affect (green) binding (inner rectangle) or import (outer circle).