Figure 6.

Functional Role of the Calcium-Binding Site

(A) Superposition of the structures of FusA^wt:fructofuranosyl-nystose (orange ribbons) and FusA^{D223A−E224A}:fructofuranosyl-nystose (green and yellow ribbons) complexes, indicating that the mutation affects only the EF hand-like motif reorienting Glu221.

(B) Growth curves of S. pneumoniae on nystose-supplemented medium. Endogenous FusA was mutated as described for each panel. No growth for the double mutant is observed on nystose.

(C) Details of the EF hand-like calcium-binding site of chain A of the FusA^{D223A−E224A}:fructo-nystose complex (yellow ribbons and sticks, with mutated residues highlighted in magenta; calcium and waters in white and red spheres, respectively); water molecules w1 = 95, w2 = 412, w3 = 284, w4 = 599, and w5 = 238 in PDB: 5G62.

(D) Normalized mean B factors for FusA:GF2 (green), FusA:GF3 (cyan), FusA:GF4 (blue), and FusA^{D223A−E224A}:GF4 (magenta-red) complexes as a function of amino acid residue, highlighting the effect on the EF-hand-like motif for FusA^D223A−E22.