Ligand hydrogen bonding

Heme x Cyto bg subunit helix A cys35 Sy bonded to carbon atom of the porphyrin s C=CH substituent (Sy-C = 1.78 A) HjO-Fe Fe axial H2O ligand hydrogen-bonded to propionate side chain of heme bn (0H2---0 = 3.50 A) and cyto be gly38 backbone amide N-H (OH2-N-H = 2.70 A) 2.53... 

Here the reversible formal potential, E° of the redox couple of interest has been measured at a series of temperatures versus a reference electrode maintained at constant temperature. Values of AShr have been interpreted in terms of differences in water-ligand hydrogen bonding [1] and have been compared to the entropy change for spin crossover in iron complexes [2]. 

Periphery Domain Networks Formed by Direct Ligand-Ligand Hydrogen Bonds Between Building Blocks... 

Table 23.3. Number of protein ligands hydrogen-bonded to water molecules [596]... 

Thrombin inhibitors (92) and (93) illustrate a novel type III peptidomimetic. Most protease inhibitors bind in an extended jS-strand conformation that is stabilized by multiple enzyme ligand hydrogen bonds. 

FIG. 9. Schematic diagram showing protein-ligand hydrogen-bonding interactions of TcTS with (A) Neu5Ac2en and (B) lactose. Ref. 145. 

From the kinetic and model studies it was postulated that the catalytic site of the P. chrysosporium MnP is located at or near the heme edge of 5-meso-carbon [87]. When the crystal structure of this MnP was elucidated, the active site was found to consist of a His ligand hydrogen bonded to an Asn residue, and a distal side peroxide binding pocket formed by a catalytic His and Arg [88]. Mn(II) binding site was shown to be at the propionate ends of the heme, Mn(II) being hexacoordinated by an Asp, two Glu residues, a heme propionate and two water molecules (Figure 14.4). 

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