Ligation single

Figure 9 Self assembly approach to de novo heme protein design, (a) bis-His ligated single heme parallel to the helices in the four a-helical bundle (b) bis-His ligated multi-hemes parallel to the helices in the four a-helical bundle. (Reprinted with permission from Ref 27. 2004 the American Chemical Society) (c) bis-His ligated multi-hemes perpendicular to each other in the four a-helical bundle. (Reprinted with permission from Ref 60. 2001 the Protein Society)...

Fig. 3. Schematic representation of mismatch repair. Recognition of the mismatches or chemically modified bases is mediated by MSH2 and MSH6 proteins that form the MutSa complex. In the next step the daughter strand is identified by non-ligated single strand breaks. MutLa complex (MLH1-MLH2) associates with MutSa, excision is performed by exonuclease I and ligation by DNA polymerase 8 (adapted from Christmann et al. 2003).

The Fe proteins are homodimers containing a single Fe4S4 cluster. Site-directed mutagenesis experiments showed that the cluster was probably held between the two subunits by ligation to two of the invariant cysteine residues from each subunit (16). This observation was confirmed later by X-ray crystallography (1) of the Fe protein... 

The molyhdopterin cofactor, as found in different enzymes, may be present either as the nucleoside monophosphate or in the dinucleotide form. In some cases the molybdenum atom binds one single cofactor molecule, while in others, two pterin cofactors coordinate the metal. Molyhdopterin cytosine dinucleotide (MCD) is found in AORs from sulfate reducers, and molyhdopterin adenine dinucleotide and molyb-dopterin hypoxanthine dinucleotide were reported for other enzymes (205). The first structural evidence for binding of the dithiolene group of the pterin tricyclic system to molybdenum was shown for the AOR from Pyrococcus furiosus and D. gigas (199). In the latter, one molyb-dopterin cytosine dinucleotide (MCD) is used for molybdenum ligation. Two molecules of MGD are present in the formate dehydrogenase and nitrate reductase. 

Figure 18.4 Structures of heme/Cu oxidases at different levels of detail, (a) Position of the redox-active cofactors relative to the membrane of CcO (left, only two obligatory subunits are shown) and quinol oxidase (right), (b) Electron transfer paths in mammalian CcO. Note that the imidazoles that ligate six-coordinate heme a and the five-coordinate heme are linked by a single amino acid, which can serve as a wire for electron transfer from ferroheme a to ferriheme as. (c) The O2 reduction site of mammalian CcO the numbering of the residues corresponds to that in the crystal structure of bovine heart CcO. The subscript 3 in heme as and heme 03 signifies the heme that binds O2. The structures were generated using coordinates deposited in the Protein Data Bank, lari [Ostermeier et al., 1997] Ifft [Abramson et al., 2000] (a) and locc [Tsukihara et al., 1996] (b, c).

Figure 10 Ribbon diagrams of a single conformer of inhibited sfSTR from residues 83 to 250. (A) The complex is viewed from above the (1-sheet. The positions of the two zincs are indicated as large balls. The strands of the [1-sheet (l-V) and helices (A-C) are indicated. The heavy atoms of the inhibitor and residues of the protein that ligate zinc are shown. The inhibitor runs antiparallel to strand IV. The structural zinc lies above the (1-sheet and is... 

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