Why zinc in zinc-fingers ?

53-55It is found that Zn complex based units are present in a number of nucleic acid binding and gene regulatory proteins. The Zn is a crucial component of the tertiary structure of "Zn-finger" since the two invariant cysteines and two invariant histidines which constitute each of the nine tandem repeats of amino acid motif are coordinated to Zn in a tetrahedral configuration (Zn-core). An attempt has been made to reason why Zn is present in "Zn-fingers" based on the assessment of the stability aspect of the core with Zn and Co

Why zinc in zinc-fingers ?

53-55It is found that Zn complex based units are present in a number of nucleic acid binding and gene regulatory proteins. The Zn is a crucial component of the tertiary structure of "Zn-finger" since the two invariant cysteines and two invariant histidines which constitute each of the nine tandem repeats of amino acid motif are coordinated to Zn in a tetrahedral configuration (Zn-core). An attempt has been made to reason why Zn is present in "Zn-fingers" based on the assessment of the stability aspect of the core with Zn and Co

Synthesis and characterization of mixed ligand complexes of Cu(II), Ni(II) and Co(II) with cytidine and amino acids

2083-2087The mixed ligand complexes of Cu(II), Ni(II) and Co(II) with cytidine and amino acids, L-alanine, L-phenylalanine and L-tryptophan have been synthesized and characterized by elemental analysis, conductivity, Infrared spectra, electronic spectral data and magnetic susceptibility measurements. In these complexes, the nucleoside acts as a monodentate ligand involving only N(3) in metal coordination whereas the amino acids acts as bidentate ligands coordinating through carboxylate oxygen and amino nitrogen. A distorted octahedral geometry for Cu(II), and octahedral geometries for both Ni(II) and Co(II) was proposed

Metal ion mediated intramolecular interactions of nuc1eosides with amino acids-Influence of stacking interactions

1008-1011Interaction of bivalent (Cu, Ni, Zn, Co, Mg and Ca) metal ions with purine nucleosides (inosine and xanthosine) and amino acids (alanine, phenylalanine and tryptophan) has been investigated by potentiometric pH measurements at 35°C and 0.10 mol dm-3 (KNO3) ionic strength. Extra stabilization has been expressed in terms of log K values. The stacking interaction observed with different amino acids and nucleosides has been discussed. Further, the influence of exocyclic substituent of xanthosine on-the stabilities is explained. Various parameters have been evaluated to rationalise the stacking interactions. No appreciable interaction is observed with Ca(II) and Mg(II)

Discriminating tendencies of cytidine and uridine towards stacking interactions – A phenomenon of biological significance

1182-1186Interaction of bivalent (Cu, Ni, Zn, C , Mg and Ca) and trivalent (La, Pr, Nd, Gd, Dy and Y) metal ions with pyrimidine nucleosides (cytidine and uridine) in the presence of amino acids (alanine, phenylalanine and tryptophan) has been investigated by potentiometric pH measurements at 35°C and 0.10 mol dm-3 (KNO3) ionic strength. Influence of charge on and the discriminating tendencies of these nuc1eosides towards stacking interactions have been discussed. Stabilization and destabilization of these ternary complexes ar quantified in terms of log K values. No interaction is observed with Mg(II) and Ca(II)

Quantitative study of hydrophobic interactions in ternary complexes involving nucleosides and amino acids

1028-1032Ternary complexes of Cu(II), Ni(II), Zn(II) and Co(II) metal ions with purine nucleosides [inosine(lno) and xanthosine (Xan)] and aliphatic amino acids [alanine (ala), α-aminobutyric acid(aba), norvaline (nor Val) and norleucine(norLeu)] have been studied in solution by potentiometric pH measurement at 35°C and 0.10 M(KNO3)ionic strength. The stabilization is expressed in terms of ∆ log K. The influence of aliphatic amino acid side chain on the stability of the complexes is discussed. Related parameters like ∆ ∆ log K, K1% of (MLA)st and ∆G° have been computed and discussed. Species distribution curves have also been obtained using the computer program BEST

Interaction of thorium(IV) and dioxouranium( VI) with histidine, cysteine and guanosine-binary and ternary complexes in solution

608-610Interaction of thoriurn(IV) and dioxouraniurn(VI) with guanosine and aminoacids, viz., histidine and cysteine in a 1 : 1 and 1 : 1 : 1 ratios has been investigated at 35°C. Stabilities of various systems are evaluated by computer program. The pH profile of various species have also been generated in order to identify the stable species at biological pH. The results suggest involvement of N(7) in guanosine, ring nitrogen and thio group in histidine and cysteine respectively along with carboxylate group in metal coordination

Quantitative aspects of intramolecular interactions in ternary complexes of purine nucleotides and amino acids

769-774Interaction Of bivalent metal ions (CO2+,Ni2+, Cu2+,Zn2+) with purine nucleotides (5' - guanosinemono-phosphate and 5' - inosinemonophonsphate) and amino acids (alanine, phenylalanine and tryptophan) in I: I and I: I: 1 ratios has been investigated by potentiometric pH measurements and formation constants in various systems are determined by computer program. The extra stabilization is expressed in terms of ∆logK. The hydrophobic interactions associated with different amino acids and nucleotides have been identified with parameters like ∆logK, Kl % of (MLA)st' and ∆Go The pH profiles of various species are generated in order to identify the stable species

Ternary complexes of cytidine and uridine-A study with bivalent and trivalent metal ions in solution

158-163Interaction of some bivalent (Cu, Ni, Zn and Co) and trivalent (La, Pr, Nd, Gd, Dy and Y) metal ions with cytidine and uridine in the presence of aminocarboxylic acids (iminodiacetic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid) has been investigated by pH measurements at 35°C and 0.10 M (KNO3) ionic strength. Influence of charge on the structure and stability of metal-nucleoside complexes has been described. The differences in the stabilities of the binary and ternary systems have been measured in terms of log K. Based on the log K values, the mode of bonding in various complexes has been discussed. The factors responsible for differences in the stabilities of cytidine and uridine ternary systems have been identified

Stability and thermodynamics of Zn(II)- cysteinemethylester and histidinemethylester system -relevance to zinc core in transcription factor IIIA

1030-1035The requirements for zinc in the regulation of gene expression is exemplified by transcription factor III A (TF III A) which is a zinc - cysteine protein, containing zinc fingers that bind to DNA. The zinc - core in this protein consisting of Zn - Cysteine - Histidine residues has an important role in the stabilization. Given the ubiquitous occurrence of zinc fingers in biological systems, the stability and thermodynamic parameters associated with the zinc - core have been assessed. The various factors that are responsible for the formation and stabilization of the core are identified