The work in this dissertation examines bacterial surface proteins, how they function to acquire heme, and how they are attached to the cell wall. The ability to obtain the macronutrient iron is a matter of life or death for almost all bacterial species. Research presented in this dissertation studies how the pathogen Staphylococcus aureus obtains this nutrient. In mammals, the majority of iron is found in heme, sequestered intracellularly within hemoproteins. To establish infections, S. aureus has evolved specialized receptors to obtain heme-iron from human hemoproteins. These receptors belong to the iron-regulated surface determinant (Isd) system, and are attached to the cell wall by the action of a cysteine transpeptidases called sortase enzymes. Research in this dissertation focuses on IsdH, the human hemoglobin (Hb) and haptoglobin (Hp) receptor. IsdH contains three " Near transporter" (NEAT) domains, which were characterized during my studies. The two N-terminal NEAT domains were found to bind methemoglobin (MetHb), Hp, and the MetHb-Hp complex, while its C-terminal NEAT domain was shown only to bind heme. The binding of different ligands by the NEAT domains suggested a model of heme transfer from MetHb. To gain insight into the mechanism of MetHb and Hp binding, the solution structure of the N-terminal NEAT domain of IsdH (IsdH^N1) was solved, revealing a novel fold not seen in other Hp- or Hb-binding proteins. Mutagenesis and binding studies were used to localize the MetHb and Hp binding site on IsdH^N1. Lastly, because we were interested in how sortases assemble the Isd system, we studied the SrtB sortase, which attaches the IsdC heme receptor to the cell wall. The NMR chemical shifts of SrtB were assigned and ¹⁵N relaxation studies were used to investigate its structure and backbone dynamics.