The regulatory role of heme in neurons.

The involvement of the metallic element iron in various biological systems is well known. In many cases, iron is employed in the form of a heme group and the family of proteins and catalytic enzymes that contain heme is well documented (e.g. the globins, cytochromes, and P450s). For many of these proteins, there is a great deal of information available in terms of structures, catalytic mechanism and function. This has led to a collective view that the main role of heme in biological systems is as a prosthetic group, binding to individual proteins and thereby conferring upon them particular functional properties. It is now becoming clear that this description represents only a part of a much more complex involvement of heme in biology and that other roles, for example in regulation and sensing, have been overlooked. This mini-review focuses on one such emerging role: the regulatory role of heme in neurons.