Models of the reduced forms of polyiron-oxo proteins: an asymmetric, triply carboxylate bridged diiron(II) complex and its reaction with dioxygen

Tolman, William B.; Liu, Shuncheng; Bentsen, James G.; Lippard, Stephen J.

doi:10.1021/ja00001a023

Cited by 125 publications

(85 citation statements)

References 8 publications

(16 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The extinction coefficient for the diiron center at 300 nm, 3240 M −1 cm −1 (on a per iron basis) was in excellent agreement with the value of 3380 M −1 cm −1 previously reported for the ferroxidase site of bacterioferritin (Yang et al 2000), and comparable to the extinction coefficients for human H‐chain ferritin, 2990 M −1 cm −1 , and horse spleen ferritin, 3540 M −1 cm −1 (Yang et al 1998). The extinction coefficient for the DF2 diiron center at 325 nm, 2400 M −1 cm −1 , compares with that of other diiron proteins: ribonucleotide reductase, 4700 M −1 cm −1 (Bollinger et al 1991) and stearoyl‐ACP Δ 9 d ‐desaturase, 2080 M −1 cm −1 (Fox et al 1994); as well as with a carboxylate/oxo‐bridged model complex, 3400 M −1 cm −1 (Tolman et al 1991).…”

Section: Resultsmentioning

confidence: 96%

Proton and metal ion‐dependent assembly of a model diiron protein

et al. 2001

View full text Add to dashboard Cite

DF1 is a small, idealized model for carboxylate-bridged diiron proteins. This protein was designed to form a dimeric four-helix bundle with a dimetal ion-binding site near the center of the structure, and its crystal structure has confirmed that it adopts the intended conformation. However, the protein showed limited solubility in aqueous buffer, and access to its active site was blocked by two hydrophobic side chains. The sequence of DF1 has now been modified to provide a very soluble protein (DF2) that binds metal ions in a rapid and reversible manner. Furthermore, the DF2 protein shows significant ferroxidase activity, suggesting that its dimetal center is accessible to oxygen. The affinity of DF2 for various first-row divalent cations deviates from the Irving-Willliams series, suggesting that its structure imparts significant geometric preferences on the metal ion-binding site. Furthermore, in the absence of metal ions, the protein folds into a dimer with concomitant binding of two protons. The uptake of two protons is expected if the structure of the apo-protein is similar to that of the crystal structure of dizinc DF1. Thus, this result suggests that the active site of DF2 is retained in the absence of metal ions. Keywords:De novo protein design; four-helix bundle; diiron; metalloprotein design Proteins use a limited set of metal ions to mediate a variety of processes. Often the same metal center can serve a number of roles; for example, binuclear iron centers engage in reversible binding of oxygen, electron transfer, and the catalysis of hydroxylation reactions (Feig and

show abstract

Section: Resultsmentioning

confidence: 96%

Proton and metal ion‐dependent assembly of a model diiron protein

et al. 2001

View full text Add to dashboard Cite

show abstract

“…In these proteins, this ferroxidase reaction 65,101 -104 results in the formation of a diferric oxo-bridged cluster characterized by a broad charge transfer transition centered near 300 nm. 105,106 The time-course of Fe(II) oxidation in the presence of DFtet (50 mM in tetramer, Figure Figure 6. Thermal denaturation curves of DFtet with and without added metal.…”

Section: Ferroxidase Reactionmentioning

confidence: 99%

Computational de novo Design, and Characterization of an A2B2 Diiron Protein

Summa

Rosenblatt

Hong

et al. 2002

Journal of Molecular Biology

126

107

View full text Add to dashboard Cite

Diiron proteins are found throughout nature and have a diverse range of functions; proteins in this class include methane monooxygenase, ribonucleotide reductase, D 9-acyl carrier protein desaturase, rubrerythrin, hemerythrin, and the ferritins. Although each of these proteins has a very different overall fold, in every case the diiron active site is situated within a four-helix bundle. Additionally, nearly all of these proteins have a conserved Glu-Xxx-Xxx-His motif on two of the four helices with the Glu and His residues ligating the iron atoms. Intriguingly, subtle differences in the active site can result in a wide variety of functions. To probe the structural basis for this diversity, we designed an A 2 B 2 heterotetrameric four-helix bundle with an active site similar to those found in the naturally occurring diiron proteins. A novel computational approach was developed for the design, which considers the energy of not only the desired fold but also alternatively folded structures. Circular dichroism spectroscopy, analytical ultracentrifugation, and thermal unfolding studies indicate that the A and B peptides specifically associate to form an A 2 B 2 heterotetramer. Further, the protein binds Zn(II) and Co(II) in the expected manner and shows ferroxidase activity under single turnover conditions.

show abstract

“…Wang and Otsuka 3,4 have studied the direct oxidation of methane to methanol using FePO 4 as the catalyst and N 2 O and H 2 /O 2 as the oxidizing agents. [8][9][10][11][12] Recently, Lee and Lippard 11 described a synthetic model with a configuration, two Fe ͑III͒ atoms connected by two hydroxo-and one carboxylate bridging groups, that reproduces the configuration of the MMO core after the substrate has been oxidized. In biological systems, the methane-methanol conversion is known to occur very efficiently.…”

Section: Introductionmentioning

confidence: 99%

Electronic spectroscopy of intermediates involved in the conversion of methane to methanol by FeO+

Aguirre

Husband

Thompson

et al. 2002

The Journal of Chemical Physics

View full text Add to dashboard Cite

Mass analyzed threshold ionization spectroscopy of 5-methylindole and 3-methylindole cations and the methyl substitution effectSpecific ion-molecule reactions are used to prepare two intermediates of the FeO ϩ ϩCH 4 reaction, and photodissociation of the jet-cooled intermediates is examined in the visible and near-ultraviolet using time-of-flight mass spectrometry. The photodissociation spectrum of the aquo iron carbene complex ͓H 2 CvFe-OH 2 ͔ ϩ shows transitions to at least four excited electronic states in the FeCH 2 ϩ chromophore, with broad vibrational structure. Photoexcitation of the insertion intermediate ͓HO-Fe-CH 3 ͔ ϩ leads to formation of FeOH ϩ ϩCH 3 and also triggers the reaction to produce Fe ϩ ϩCH 3 OH. The photodissociation spectrum of ͓HO-Fe-CH 3 ͔ ϩ presents a vibrationally resolved band involving progressions in the excited state Fe-C stretch, Fe-O stretch, and O-Fe-C bend. The change in the Fe-C bond length in ͓HO-Fe-CH 3 ͔ ϩ and ͓H 2 CvFe-OH 2 ͔ ϩ upon photoexcitation is calculated from a Franck-Condon analysis of the vibronic features observed. The analysis of the experimental results is aided by hybrid Hartree-Fock/density-functional ͑B3LYP͒ calculations on ͓HO-Fe-CH 3 ͔ ϩ and ͓H 2 CvFe-OH 2 ͔ ϩ performed to determine molecular parameters, and time-dependent density functional theory ͑TD-DFT͒ calculations on FeCH 2 ϩ to predict excited electronic states.

show abstract

Models of the reduced forms of polyiron-oxo proteins: an asymmetric, triply carboxylate bridged diiron(II) complex and its reaction with dioxygen

Cited by 125 publications

References 8 publications

Proton and metal ion‐dependent assembly of a model diiron protein

Proton and metal ion‐dependent assembly of a model diiron protein

Computational de novo Design, and Characterization of an A2B2 Diiron Protein

Electronic spectroscopy of intermediates involved in the conversion of methane to methanol by FeO+

Contact Info

Product

Resources

About