Putting Metal in the Middle
Placing metal ions into the center of a porphyrin ring is a significant cellular challenge. Lundqvist et ai. (2010) provide snapshots of the AAA + motor unit of magnesium chelatase, an enzyme that insert magnesium ion into the porphyrin ring accompanied by ATP expenditure, in different states of binding to adenosyl nucleotides.
David Bollivar. "Putting Metal in the Middle" Structure 18 (2010): 1-2.
Available at: http://works.bepress.com/david_bollivar/14