Receptor mapping with artificial siderophores
In order to guarantee adequate supply of iron, which is essential for growth, microbial organisms have developed ingenious vehicles, the siderophores. These low molecular weight compounds bind and transport iron from the environment into the cell in a receptor driven mechanism. In an attempt to simulate the properties of one of the siderophoresferrichrome, with artificial binders, tripod-like hydroxamates that bind iron(II1) in the same configuration as the natural counterpart with equal growth promotion activity were prepared. In vivo tests of these compounds established that three of them approach and even equal the activity of genuine ferrichrome BS growth promoters of Arthrobacter flavescens. A. flavescens is completely dependent on ferrichrome for growth and previously failed to respond to any synthetic compounds. The biomimetic iron carriers described here are thus the first examples that are active towards this mutant and are taken up by a receptor driven mechanism. The implications of these findings in mapping the surface of siderophore receptors are discussed.