Thematic minireview series: metals in biology 2010.

Metals are present in nearly one-half of protein structures analyzed to date and play important roles in many of these enzymes. This prologue introduces the third of the Thematic Minireview Series on Metals in Biology, which is focused on iron homeostasis. The four minireviews in the current series deal with redox cycling in iron metabolism, the biogenesis and assembly of iron-sulfur centers (two articles), and the assembly of iron into heme.