Putting metal in the middle.
Placing metal ions into the center of a porphyrin ring is a significant cellular challenge. Lundqvist et al. (2010) provide snapshots of the AAA+ motor unit of magnesium chelatase, an enzyme that inserts a magnesium ion into the porphyrin ring accompanied by ATP expenditure, in different states of binding to adenosyl nucleotides.
Bollivar
David W
DW