Synthesis and structural modeling of the amphiphilic siderophore rhizobactin-1021 and its analogs

Synthesis of Biosynthetic Intermediates of Vibrioferrin and Enzyme Reactions Using Them as Substrates

Biosynthetic intermediates of siderophore vibrioferrin (VF), O-citryl-L-serine, 2-aminoethyl citrate, and alanine-2-amidoethyl citrate were respectively synthesized as a mixture of stereoisomers. These compounds were used as substrates for enzyme reactions using recombinant PvsA, PvsB, and PvsE proteins as corresponding enzyme equivalents. The results of our study show that each enzyme reacts with a respective substrate and produces VF along the proposed biosynthetic pathway. Furthermore, the results of this study will contribute to the understanding of VF biosynthetic enzymes and may help in the development of antimicrobial drugs by inhibiting siderophore biosynthetic enzymes.

Enzymatic tailoring of enterobactin alters membrane partitioning and iron acquisition

Enterobactin (Ent), a prototypic bacterial siderophore, is modified by both the C-glucosyltransferase IroB and the macrolactone hydrolase IroE in pathogenic bacteria that contain the iroA cluster. To investigate the possible effects of glucosylation and macrolactone hydrolysis on the physical properties of Ent, the membrane affinities and iron acquisition rates of Ent and Ent-derived siderophores were measured. The data obtained indicate that Ent has a high membrane affinity (K(x) = 1.5 x 10(4)) similar to that of ferric acinetoferrin, an amphiphile containing two eight-carbon hydrophobic chains. Glucosylation and macrolactone hydrolysis decrease the membrane affinity of Ent by 5-25-fold. Furthermore, in the presence of phospholipid vesicles, the iron acquisition rate is significantly increased by glucosylation and macrolactone hydrolysis, due to the resultant decrease in membrane sequestration of the siderophore. These results suggest that IroB and IroE enhance the ability of Ent-producing pathogens to acquire iron in membrane-rich microenvironments.