Iron-binding groups

Fig. 1. Common siderophore iron-binding groups catechol (Eq. (4)), hydroxamic acid (Eq. (5)), ot-hydroxycarboxylic acid (Eq. (6)), and hydroxypyridinone (Eq. (7)). Additional siderophore binding groups ...

In positions so that six stable bonds can be formed to chelate Iron. Such a molecule Is desferrioxamlne or Desferal three hydroxamlc acids are separated by several carbons to provide adequate spacing for the Iron binding groups along with several additional oxygens and nitrogens to make the molecule more water soluble. This Iron chelator Is effective In man. 

NifA proteins are of one of two types. One group consists of 02-sensitive NifA proteins, which are found in the rhizobia Bhodobacter and Ae spirillum. These proteins have a proposed iron-binding motif on a linker between the central and C-terminal domains that may form a redox-sensitive... 

Another study of a synthetic siderophore analog of mixed cathechol and hydroxamate donor groups exhibited similar spectral shifts with pH as observed for tris-catecholate side-rophores, consistent with a salicylate-binding mode shift (102). While this synthetic siderophore mimic supports the growth of many species of bacteria, it also exhibits a low iron-binding affinity relative to other hexadentate siderophores, with a pFe value of 18.3 (see L(cat2hydroxamate) Table HE). 

A more complex set of 1,3,5-benzenetricarboxamids, composed of mono- di- and tritopic iron chelating groups, prepared by Tsubouchi and coworkers", showed that tripodal hydroxamates 47 and 48 were able to form tripodal interstrand complexes with one and two iron(III) ions. The tritopic hydroxamate 49 formed preferably ferrioxamine-like intrastrand structures, where each arm binds an iron(III) ion independently. No microbial activity was reported for 47-49. 

An 80- to 90-residue N-terminal propeptide domain contains a cysteine whose -S group binds to the active site zinc, screening it from potential substrates. The central catalytic domain is followed by a hinge region and a C-terminal domain that resembles the serum iron binding and transporting hemopexin.427/436 The mechanism of action is probably similar to that of thermolysin.430... 

Transferrin of blood plasma is encoded by a separate gene but has a similar structure. Transferrin of chickens appears to be identical to conalbumin of egg whites. The iron-binding proteins of body fluids are sometimes given the group name siderophilins. Transferrins may function not only in transport of iron throughout the body but also as iron buffers that provide a relatively constant iron concentration within tissues. 

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