Publisher Summary This chapter compares the structures of the iron cores and protein coats of ferritins and the hemoferritins of bacteria, and the current state of knowledge concerning mineralization processes in these molecules is discussed in relation to this structural information. Iron—because of its abundance and versatility—has become an essential element for virtually all forms of life. It is found in enzymes with a variety of functions—for example, ribonucleotide reductase, aconitase, nitrogenase, catechol dioxygenase, acid phosphatase, and procollagen proline hydroxylase and in several of the electron transfer proteins of respiration and photosynthesis. Iron may be the prosthetic group of fumarate nitrate reductase (FNR), a transcriptional regulator for oxygen-dependent gene expression in Escherichia coli. Bacterial ferritin (bacterioferritin) may also be involved in regulating levels of free iron within the cell once the iron has been taken up.
