Simple inorganic structures comprised of iron and sulfur are called [Fe-S] clusters. They likely represent one of the earliest prosthetic groups associated with the emergence of life on earth and continue to have essential roles in sustaining many metabolic processes in almost all existing life forms. For example, proteins that contain one or more [Fe-S] clusters, generally referred to as [Fe-S] proteins, are involved in a wide variety of important cellular functions, including energy transformations, catalysis, and regulation of gene expression.
