Structure and Properties of [Fe4S4{2,6-bis(acylamino)benzenethiolato-S}4]2- and [Fe2S2{2,6-bis(acylamino)benzenethiolato-S}4]2-:  Protection of the Fe−S Bond by Double NH···S Hydrogen Bonds

Ueyama, Norikazu; Yamada, Yusuke; Ta, Okamura; Kimura, Shunta; Nakamura, Akira

doi:10.1021/ic9604324

Cited by 85 publications

(96 citation statements)

References 62 publications

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“…These early studies indicated that this proximal hydrogen bond could be the link between changes in midpoint potentials and the reactivity of the iron atom (56,57). Later on, model studies conducted by Ueyama et al (58) suggested that the NH-S hydrogen bond of ferredoxin model complexes contributed to the redox potential of the Fe-S center. More recent approaches utilizing site-directed mutagenesis confirmed that these relationships hold true for a number of enzyme systems, including peroxidases (59) and cytochrome P450 (46, 60 -62).…”

Section: Discussionmentioning

confidence: 99%

Influence of Heme-Thiolate in Shaping the Catalytic Properties of a Bacterial Nitric-oxide Synthase

Hannibal

Ramasamy

Tejero

et al. 2011

Journal of Biological Chemistry

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Background: NOSs possess a highly conserved tryptophan residue, proximal to the heme-thiolate bond. Results: Replacement of this Trp by His or Phe in Bacillus subtilis NOS altered both thermodynamic and kinetic parameters and NO synthesis. Conclusion: B. subtilis NOS control catalysis by tuning the electron density of its heme-thiolate bond. Significance: This is the first study to investigate these relationships in a bacterial NOS.Nitric-oxide synthases (NOS) are heme-thiolate enzymes that generate nitric oxide (NO) from L-arginine. Mammalian and bacterial NOSs contain a conserved tryptophan (Trp) that hydrogen bonds with the heme-thiolate ligand. We mutated Trp 66 to His and Phe (W66H, W66F) in B. subtilis NOS to investigate how heme-thiolate electronic properties control enzyme catalysis. The mutations had opposite effects on heme midpoint potential (؊302, ؊361, and ؊427 mV for W66H, wild-type (WT), and W66F, respectively). These changes were associated with rank order (W66H < WT < W66F) changes in the rates of oxygen activation and product formation in Arg hydroxylation and N-hydroxyarginine (NOHA) oxidation single turnover reactions, and in the O 2 reactivity of the ferrous heme-NO product complex. However, enzyme ferrous heme-O 2 autoxidation showed an opposite rank order. Tetrahydrofolate supported NO synthesis by WT and the mutant NOS. All three proteins showed similar extents of product formation (L-Arg 3 NOHA or NOHA 3 citrulline) in single turnover studies, but the W66F mutant showed a 2.5 times lower activity when the reactions were supported by flavoproteins and NADPH. We conclude that Trp 66 controls several catalytic parameters by tuning the electron density of the heme-thiolate bond. A greater electron density (as in W66F) improves oxygen activation and reactivity toward substrate, but decreases heme-dioxy stability and lowers the driving force for heme reduction. In the WT enzyme the Trp 66 residue balances these opposing effects for optimal catalysis.Nitric oxide (NO) is a small molecule essential to life in higher organisms. In mammals, NO synthesis is performed by three isoforms (inducible, endothelial, and neuronal) of homodimeric nitric-oxide synthases (NOS, EC 1.14.13.39). Each monomer is comprised of a nitric-oxide synthase oxygenase domain (NOSoxy), 3 with structurally defined binding sites for its substrate L-arginine, tetrahydrobiopterin (H 4 B), and a Cyscoordinated Fe-protoporphyrin IX moiety (heme), and a C-terminal reductase domain (NOSred) with binding sites for NADPH, FAD, and FMN. NOSoxy and NOSred are connected by a calmodulin binding sequence (1, 2).The existence of NOS is not unique to animals. A number of bacterial NOS or NOS-like proteins have been isolated and characterized during the past 10 years . With the exception of the complete NOS present in Sorangium cellulosum (25), all of the bacterial NOSs characterized to date consist of a truncated NOSoxy domain that lacks a portion of the N-terminal region and has no attached reductase domain (30). Thus, NO synthesis by bact...

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Section: Discussionmentioning

confidence: 99%

Influence of Heme-Thiolate in Shaping the Catalytic Properties of a Bacterial Nitric-oxide Synthase

Hannibal

Ramasamy

Tejero

et al. 2011

Journal of Biological Chemistry

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“…4), but the lower overall steric demand of A (Me) relative to V (Pr i ) allows the protein chain to move towards the iron site, shortening the 44NH777S42 distance by 0.4(1) Å, consistent with introduction of a hydrogen bond. Consequently, a minor change in the steric requirements of a surface residue has led to a positive shift in E7 of 50 mV [9,37]. Such NH777Sg hydrogen bonds appear to contain significant covalent character and have been proposed to provide specific low-energy pathways for electron transfer from metal centres [38,39].…”

Section: Electrochemistry Of Rd Proteinsmentioning

confidence: 99%

Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum : solvent access versus structural changes as determinants of reversible potential

Xiao¹,

Maher

Cross³

et al. 2000

J Biol Inorg Chem

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The Pr(i) sidechains of two adjacent valine residues, V8 and V44, define the surface of the rubredoxin from Clostridium pasteurianum and control access to its Fe(S-Cys)4 active site. To assess the effect of systematic change of the steric bulk of the alkyl sidechains, eight single and three double mutant proteins have been isolated which vary G (H), A (Me), V (Pr(i)), L (Bu(i)) and I (Bu(s)) at those positions. X-ray crystal structures of the Fe(III) forms of the V44A and V44I proteins are reported. Positive shifts in reversible potential of up to 116 mV are observed and attributed to increased polarity around the Fe(S-Cys)4 site induced by (1) changes in protein backbone conformation driven by variation of the steric demands of the sidechain substituents and (2) changes in solvent access to the side-chains of ligands C9 and C42. Data for the V44A mutant show that a minor change in the steric requirements of a surface residue can introduce a NH...Sgamma hydrogen bond at the active site and lead to a shift in potential of + 50 mV.

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“…A greater understanding of S‚‚‚H bonding may have fundamental importance in biochemical research in understanding and predicting protein folding and biomolecular interactions. 7 Several hydrogen-bonded supramolecular studies have focused on molecules with C 3 symmetry, due to their ability to form highly organized, extended structures. 8 In a like manner, the D 3h -symmetric molecule trimercaptotriazine was used to explore the nature and extent of S‚‚‚H bonding and implications of this interaction to supramolecular chemistry in hydrogen-bonded complexes with the amines pyrrolidine, triethylamine, propylenediamine, ethylenediamine, and pyridine.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bonding with Sulfur

Krepps

Parkin

Atwood

2001

Crystal Growth & Design

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ABSTRACT:The hydrogen-bonding capabilities of the sulfur-containing molecule trimercaptotriazine (TMT) was explored using various amines. The amines were chosen to observe the effect of varying base strength on the resulting hydrogen-bonded structures. (5) were characterized by melting point, elemental analysis, infrared spectroscopy, and X-ray crystallography. It was found that the TMT molecule is readily deprotonated by all of the amines and that the subsequent ammonium hydrogens formed several types of hydrogen bonds. Importantly, these bonds were observed to form with the sulfur atoms of the TMT, with S‚‚‚N distances of 3.3-3.5 Å.

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Structure and Properties of [Fe₄S₄{2,6-bis(acylamino)benzenethiolato-S}₄]²^- and [Fe₂S₂{2,6-bis(acylamino)benzenethiolato-S}₄]²^-: Protection of the Fe−S Bond by Double NH···S Hydrogen Bonds

Cited by 85 publications

References 62 publications

Influence of Heme-Thiolate in Shaping the Catalytic Properties of a Bacterial Nitric-oxide Synthase

Influence of Heme-Thiolate in Shaping the Catalytic Properties of a Bacterial Nitric-oxide Synthase

Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum : solvent access versus structural changes as determinants of reversible potential

Hydrogen Bonding with Sulfur

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