Structure similarities with bacterial binding

Kuryatov, A., Laube, B., Betz, H., and Kuhse, J. (1994). Mutational analysis of the glycine-binding site of the NMDA receptor Structural similarity with bacterial amino acid-binding proteins. Neuron 12, 1291-1300. 

Given this structural similarity, it should not be surprising to learn that sulfanilamide competes with p-aminobenzoic acid for a binding site on the surface of dihydropteroate synthetase. Put another way, sulfanilamide binds to the enzyme where p-aminobenzoic acid should bind but no reaction occurs. The consequence is that a step in folic acid biosynthesis is disrupted and the bacterial cell is deprived of adequate folic acid. Nucleic acid synthesis, among other things, is disrupted, leading to a cessation of cell growth and division. The human immune system can mop up what remains. No similar consequences befall the human host since it cannot make folic acid in the first place and must get an adequate supply of this vitamin in the diet. 

A remarkable feature of transferrin structure, discovered when the human lactoferrin structure was determined (67, 85), is the striking similarity with a group of bacterial binding proteins. These proteins, the bacterial periplasmic binding proteins, bind and transport certain small molecules, such as sugars, amino acids and oxyanions, through the periplasmic space before delivering them via specific receptors in the bacterial cell wall (111). They thus share with transferrins the... 

As noted in Section 3, some pathogenic bacteria have transferrin receptors on their outer membranes to acquire diferric transferrin from their host. These outer membrane receptors extract the iron from the transferrin and transport it into the periplasm where it is picked up by the periplasmic ferric binding proteins (Fbp), which carry the iron to a transmembrane protein in the inner membrane that conveys it into the cytoplasm. A considerable amount of chemical and structural information has been gathered for Fbp, which is sometimes referred to as bacterial transferrin in recognition of its similarities with animal transferrin. ... 

---