Zinc-ligand interactions

The 12 residues between the second cysteine zinc ligand and the first histidine ligand of the classic zinc finger motif form the "finger region". Structurally, this region comprises the second p strand, the N-terminal half of the helix and the two residues that form the turn between the p strand and the helix. This is the region of the polypeptide chain that forms the main interaction area with DNA and these interactions are both sequence specific. 

The two zinc ions fulfill important but different functions in the DNA-binding domains. The first zinc ion is important for DNA-bindlng because it properly positions the recognition helix the last two cysteine zinc ligands are part of this helix. The second zinc ion is important for dimerization since the five-residue loop between the first two cysteine zinc ligands is the main component of the dimer interaction area. 

Sanders (83) constructed a supramolecular assembly of heterometal-lic porphyrins held together by different types of metal-ligand interaction. The team exploited the different kinetic and thermodynamic properties of the pyridine-zinc, carboxylate-tin, and pyridine-... 

Hydrogen bond interactions are important for the function of histidine as a zinc ligand. For example, in a survey of zinc-binding motifs, Christianson and Alexander (1989, 1990) reported that head-on and... 

The amino acid side chains which serve as zinc ligands in a metallo-protein are densely packed within the protein structure and often make hydrogen bond contacts with other residues. Argos et al. (1978) pointed out that such interactions orient the metal ligands, and these interactions may also enhance the electrostatic interaction between the metal ion and its ligands. 

Excess copper is toxic to cells. On one hand, copper ions can avidly bind to biomolecules by ligand interaction with cysteines or by binding to histidine-rich regions. Copper ions could also be incorporated into proteins instead of zinc or other metal ions during biosynthesis. On the other hand, copper ions can form radicals by a Fenton-type reaction as shown in Eq. (1) ... 

Zinc finger proteins have recently been classified into eight distinct structural groups distinguished by their tertiary structural folds around the zinc coordination complex and the spatial arrangement of secondary structural elements that contribute zinc ligands. Table 1 lists representative members from each of six of these eight stmctural classes that are known to interact directly with nucleic acids. These are discussed in turn. 

These secondary ligand interactions will likely effect the stability of the zinc site, the dissociation rate constant for zinc and the manner in which zinc participates in catalysis. Thus disruption of these interactions could lead to weakened... 

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