Metallothionein is a ubiquitous protein with a wide range of proposed physiological roles, including the transport, storage and detoxification of essential and nonessential trace metals. The amino acid sequence of isoform 2a of rabbit liver metallothionein, the isoform used in our spectroscopic studies, includes 20 cysteinyl groups out of 62 amino acids. Metallothioneins in general represent an...

The structural basis of the regulation of microsomal cytochrome P450 (P450) activity was investigated by mutating the highly conserved heme binding motif residue, Phe429, on the proximal side of cytochrome P450 2B4 to a histidine. Spectroscopic, pre-steady-state and steady-state kinetic, thermodynamic, theoretical, and structural studies of the mutant demonstrate that formation of an H-bond bet...

Nitric-oxide synthases (NOS) are heme-thiolate enzymes that N-hydroxylate L-arginine (L-Arg) to make NO. NOS contain a unique Trp residue whose side chain stacks with the heme and hydrogen bonds with the heme thiolate. To understand its importance we substituted His for Trp188 in the inducible NOS oxygenase domain (iNOSoxy) and characterized enzyme spectral, thermodynamic, structural, kinetic, ...

113Cd-NMR studies have been used to elucidate the structure of the metal-binding sites in mammalian and invertebrate ( Scylla serrata) metallothioneins (MTs). Chemical shift data have shown that all Cd ions are tetrahedrally coordinated to four cysteine thiolate ligands with single cysteinyl sulfurs bridging adjacent metals. Homonuclear decoupling experiments have shown that the 7 g-atoms of me...

Zinc (Zn) is one of the most abundant metals and is essential for life. Through ligand interactions, often with thiolate from cysteine residues in proteins, Zn can play important structural roles in organizing protein structure and augmenting protein folding and stability. However, it is difficult to separate the contributions of Zn-ligand interactions from those originating from intrinsic prot...

Metal sulfide minerals are assumed to form naturally at ambient conditions via reaction of a metallic element with (poly)sulfide ions, usually produced by microbes in oxygen-depleted environments. Recently, the formation of mercury sulfide (β-HgS) directly from linear Hg(II)-thiolate complexes (Hg(SR)2) in natural organic matter and in cysteine solutions was demonstrated under aerated condition...

863-Pos Board B632 Hydrogen Bond Strength Modulates the Mechanical Strength of FerricThiolate Bonds in Rubredoxin Peng Zheng, Shin-ichi J. Takayama, A Grant Mauk, Hongbin Li. University of British Columbia, Vancouver, BC, Canada. It has long been recognized that hydrogen bonds formed by protein backbone amides with cysteinyl Sulfur atoms play important roles in modulating the functional and str...

The resolution of new features in the 1H electron nuclear double resonance (ENDOR) spectrum of the oxidized CuA site in beef heart cytochrome c oxidase is presented. In a previous study, we assigned resonances in the CuA ENDOR spectrum to hyperfine interactions of methylene protons on one or two cysteine ligands to CuA (Stevens, T.H., Martin, C.T., Wang, H., Brudvig, G.W., Scholes, C.P., and Ch...

Bacillus megaterium flavocytochrome P450 BM3 is a catalytically self-sufficient fatty acid hydroxylase formed by fusion of soluble NADPH-cytochrome P450 reductase and P450 domains. Selected mutations at residue 264 in the haem (P450) domain of the enzyme lead to novel amino acid sixth (distal) co-ordination ligands to the haem iron. The catalytic, spectroscopic and thermodynamic properties of t...

The knowledge of the structural evolution among thiolate-protected gold nanoclusters is not only helpful for understanding their structure-property relationship but also provides scientific evidence to rule-guided structure predictions gold...