Diiron carboxylate proteins

As mentioned in Sect. 5.3.3, a number of enzymes contain metal ions that participate in the catalytic reaction. Two specialized databases store information on metal ions and other bioinorganic motifs in enzymes. PROMISE (prosthetic centers and metal ions in protein active sites) is maintained by the University of Leeds and focuses on six major groups of metal containing proteins diiron-carboxylate proteins, haem proteins, iron-sulfur proteins, molybdopterin proteins, mononuclear iron proteins, and chlorophyll containing proteins156. ... 

It is the reduced states of diiron carboxylate proteins that react with dioxygen. Accordingly, we, and others, have begun to explore the fundamental chemistry of diiron(II) model complexes with dioxygen as an approach to understanding the diverse reactivity of these proteins. Examples of diiron(II) model compounds described in the literature are presented in Figure For... 

Berthold DA, Stenmark P. 2003. Membrane-bormd diiron carboxylate proteins. Annu Rev Plant Biol 54 497-517. 

E. Y. Tshuva, S. J. Lippard, Synthetic models for non-heme carboxylate-bridged diiron metaUo-proteins Strategies and tactics, Chem. Rev. 104 (2004) 987. 

The final class of iron proteins that we consider here are a family that contain a carboxylate-bridged diiron centre. They carry out a variety of functions, which have the common link that they react with dioxygen as part of their functional processes. The dimetallic centre is incorporated into a four-helix bundle domain (see Figure 3.9a), which seems to represent... 

The best characterized of the BMMs are the sMMOs (Figure 13.24), which are the only members of the family capable of activating the inert C-H bond of methane, one of the most difficult reactions in nature to achieve. Like most members of the BMM superfamily, sMMO requires three protein components, the hydroxylase MMOH, which contains the carboxylate-bridged diiron centre, a regulatory protein MMOB and a [2Fe-2S]- and FAD-containing reductase (MMOR) which shuttles electrons from NADH to the diiron centre. 

Figure 13.26 Dioxygen-utilizing carboxylate-bridged diiron centres (a) Oxidized (top) and reduced (bottom) MMOH (b) oxidized (top) and Mnn-reconstituted ToMOH (bottom) (c) oxidized (top) and reduced (bottom) RNR-R2 (d) oxidized (top) and reduced (bottom) rubryerythrin (e) reduced stearoyl-acyl carrier protein A9 desaturase (f) reduced bacterioferritin (g) methaemerythrin. Fel is on the left and Fe2 on the right. (Reprinted with permission from Sazinsky and Lippard, 2006. Copyright (2006) American Chemical Society.)...

Because of the ubiquitous presence of bridging carboxylato groups, they are also known as carboxylate-bridged non-heme iron proteins. They are known for a large number of nuclearities which range from one iron center to many iron centers the most common contain the diiron unit. Several of these metalloenzymes are involved... 

Tolman, W. B., Liu, S., Bentsen, J. G., and Lippard, S. J., 1991, Models of the reduced forms of polyiron-oxo proteins An asymmetric, triply carboxylate bridged diiron(ll) complex and its reactions with dioxygen, J. Am. Chem. Soc. 113 1529164. 

Metalloenzymes with diiron sites where the metal ions are bridged by carboxylates (i.e. glutamate, aspartate) have emerged as an important class of enzyme see Iron Proteins with Dinuclear Active Sites)Several members of this... 

Figure 11 (a) Protein backbone tracing of the D. vulgaris Rbr head-to-taiT homodimer viewed along its twofold rotation axis drawn using RASMOL and coordinates from IRYT in the Protein Data Bank. Amino (N) and carboxyl (C) termini are labeled, iron atoms are represented as spheres, and dashed lines indicate subunit interface regions between the [Fe(SCys)4] and diiron sites, (b) Schematic structures of the diiron sites and submit interfaces from the all-ferric and all-ferrons Rbr X-ray crystal strucmres. (Reprinted with permission from Refs. 68 69. 2002 2003 American Chemical Society)... 

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