Conformation metal binding

The ion channels which permit transport of ions, are constructed from protein polymers in helical conformations. These helices form the wall of cell channels and their precise conformations result in specific geometrical arrangements of a number of potential ligand-metal binding sites. There are striking differences between the channels, selective towards either Na+ or K+ ions. 

Enolase has a complex metal ion requirement,683 69 usually met by Mg2+ and Mn2+. From NMR studies of the relaxation of water protons, it was concluded that a Mn2+ ion coordinates two rapidly exchangeable water molecules in the free enzyme. When substrate binds, one of these water molecules may be immobilized and may participate in an addition reaction that forms phosphoenolpyruvate (reverse of reaction 13-15). A tightly bound "conformational" metal ion is located in the known three-dimensional structure in such a... 

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