Study on the heme acquisition system A from Pseudomonas aeruginosa and its functionalization
Bacteria have developed several iron scavenging mechanisms to assimilate sufficient amounts of iron to survive. One of systems developed by some Gram-negative pathogens such as Pseudomonas aeruginosa to acquire iron from their hosts involves secretion of a small protein hemophore known as HasA. The function of hemophores is to capture the heme, either from solution or from heme containing proteins, and to deliver it to the hemophore specific receptor, HasR. HasA binds heme so tightly (Ka = 5.3 × 1010 M-1) and delivers it to outer membrane recepter, HasR. HasA binds heme using two loops including histidine-32 and tyrosine-75 as ligands for the heme iron. The structure of the loop including histidine-32 is drastically changed after the heme binding. This loop appears to be important for the heme acquisition and release.