Part of an ATP-driven transport system for iron. Metal-binding component (Potential). Acts as an adhesin that promotes binding of H.influenzae to host laminin and vitronectin. In addition, interaction with serum vitronectin plays an important role in bacterial serum resistance. Interacts with host laminin and vitronectin. Can interact with both immobilized and soluble vitronectin. Mutant displays a reduced binding to laminin, vitronectin, and epithelial cells, and is more sensitive to killing by human serum compared with the wild type. Belongs to the bacterial solute-binding protein 9 family.