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. Author manuscript; available in PMC: 2014 Jun 2.
Published in final edited form as: Front Biol (Beijing). 2014 Jan 2;9(2):104–113. doi: 10.1007/s11515-014-1302-6

Figure 1.

Figure 1

The proposed pathways for biosynthesis and maintenance of the FeIII2-Y• cofactor of class Ia RNR. The biosynthetic pathway requires delivery of two FeII and a reducing equivalent (electron) per β subunit to carry out the four-electron reduction of O2 to H2O (Eq. (1)). The other three electrons come from the two FeII and Tyr residue to form the FeIII2-Y•. The maintenance pathway may use the same source of reducing equivalents to convert the inactive FeIII2-Y cluster to FeII2-Y, which subsequently forms FeIII2-Y• in the presence of O2 via the biosynthetic pathway.