Chelating agents coordination structure

The extracellular domain of cadherins consists of a variable number of a repeated sequence of about 110 amino acids. This sequence is termed the cadherin repeat and resembles in overall structure, but not in sequence, the Ig like domains. The cadherin repeat is the characteristic motive common to all members of the cadherin superfamily. Classical and desmosomal cadherins contain five cadherin repeats, but as many as 34 repeats have been found in the FAT cadherin (see below). Cadherins are calcium-dependent cell adhesion molecules, which means that removal of Ca2+, e.g., by chelating agents such as EDTA, leads to loss of cadherin function. The Ca2+-binding pockets are made up of amino acids from two consecutive cadherin repeats, which form a characteristic tertiary structure to coordinate a single Ca2+ion [1]. 

Chelating agents can coordinate with metal ions at a minimum of two sites. Typically this bidentate coordination solubilizes or otherwise inactivates these metal ions. The effect is to counter any deleterious actions these metals might have on the system in which the chelates are used. The chelating agents form ring structures that incorporate the metal ion within the molecule250. 

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