scholarly journals Conservation of the structural and functional architecture of encapsulated ferritins in bacteria and archaea

2018 ◽  
Author(s):  
Didi He ◽  
Cecilia Piergentili ◽  
Jennifer Ross ◽  
Emma Tarrant ◽  
Laura R. Tuck ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Rhodospirillum Rubrum ◽  
Quaternary Structure ◽  
Pyrococcus Furiosus ◽  
Essential Element ◽  
Wide Distribution ◽  
High Reactivity ◽  
Iron Store ◽  
Fenton Chemistry ◽  
Ferroxidase Activity

ABSTRACTIron is an essential element for many biological processes; however, due to its high reactivity iron can also be very toxic, producing reactive oxygen species through Fenton chemistry. Ferritins protect the cell from oxidative stress by catalytically converting Fe(II) into less toxic Fe(III) and storing the resulting iron minerals within their core. Encapsulated ferritins (EncFtn) are a sub-family of ferritin-like proteins, which are widely distributed in all bacterial and archaeal phyla. We recently characterised the Rhodospirillum rubrum EncFtn, showing that although enzymatically active, due to its open structure it requires the association with an encapsulin nanocage in order to act as an iron store. Given the wide distribution of the EncFtn family in organisms with diverse environmental niches, a question arises as to whether the structure and catalytic activity is conserved across the family. Here we structurally characterise two EncFtn members from the halophile Haliangium ochraceum and the thermophile Pyrococcus furiosus, which show the same distinct annular decamer topology observed in R. rubrum EncFtn, with the ferroxidase centre (FOC) formed between one of the dimer interfaces. Solution and native mass spectrometr analyses show that the stability of the protein quaternary structure differs between EncFtn proteins from different species. The catalytic role of the EncFtn proteins was confirmed by biochemical assays, and we show that Zn(II) ions inhibit the ferroxidase activity of the EncFtn proteins to varying degrees. Our results represent a further step in the characterisation of the recently discovered EncFtn ferritin-like sub-family, indicating a common structural organisation and catalytic activity, despite diverse host environments.

scholarly journals Conservation of the structural and functional architecture of encapsulated ferritins in bacteria and archaea

2019 ◽  
Vol 476 (6) ◽  
pp. 975-989 ◽  
Author(s):  
Didi He ◽  
Cecilia Piergentili ◽  
Jennifer Ross ◽  
Emma Tarrant ◽  
Laura R. Tuck ◽  
...  
Keyword(s):  
Metal Binding ◽  
Rhodospirillum Rubrum ◽  
Quaternary Structure ◽  
Pyrococcus Furiosus ◽  
Large Family ◽  
Native Mass Spectrometry ◽  
Wide Distribution ◽  
Iron Store ◽  
Unusual Structure ◽  
Ferroxidase Activity

Abstract Ferritins are a large family of intracellular proteins that protect the cell from oxidative stress by catalytically converting Fe(II) into less toxic Fe(III) and storing iron minerals within their core. Encapsulated ferritins (EncFtn) are a sub-family of ferritin-like proteins, which are widely distributed in all bacterial and archaeal phyla. The recently characterized Rhodospirillum rubrum EncFtn displays an unusual structure when compared with classical ferritins, with an open decameric structure that is enzymatically active, but unable to store iron. This EncFtn must be associated with an encapsulin nanocage in order to act as an iron store. Given the wide distribution of the EncFtn family in organisms with diverse environmental niches, a question arises as to whether this unusual structure is conserved across the family. Here, we characterize EncFtn proteins from the halophile Haliangium ochraceum and the thermophile Pyrococcus furiosus, which show the conserved annular pentamer of dimers topology. Key structural differences are apparent between the homologues, particularly in the centre of the ring and the secondary metal-binding site, which is not conserved across the homologues. Solution and native mass spectrometry analyses highlight that the stability of the protein quaternary structure differs between EncFtn proteins from different species. The ferroxidase activity of EncFtn proteins was confirmed, and we show that while the quaternary structure around the ferroxidase centre is distinct from classical ferritins, the ferroxidase activity is still inhibited by Zn(II). Our results highlight the common structural organization and activity of EncFtn proteins, despite diverse host environments and contexts within encapsulins.

Quaternary Structure and Catalytic Activity of theEscherichia coliRibonuclease E Amino-Terminal Catalytic Domain†

Biochemistry ◽  
2003 ◽  
Vol 42 (47) ◽  
pp. 13848-13855 ◽  
Author(s):  
Anastasia J. Callaghan ◽  
J. Günter Grossmann ◽  
Yulia U. Redko ◽  
Leopold L. Ilag ◽  
Martin C. Moncrieffe ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Quaternary Structure ◽  
Catalytic Domain ◽  
Amino Terminal

scholarly journals Dissecting the structural and functional roles of a vicinal iron-binding site in encapsulated ferritins

2019 ◽  
Author(s):  
Cecilia Piergentili ◽  
Jennifer Ross ◽  
Didi He ◽  
Kelly J. Gallagher ◽  
Will A. Stanley ◽  
...  
Keyword(s):  
Binding Site ◽  
Metal Binding ◽  
Rhodospirillum Rubrum ◽  
Catalytic Mechanism ◽  
Iron Oxidation ◽  
Functional Study ◽  
Secondary Site ◽  
Iron Store ◽  
Entry Site ◽  
Ferroxidase Center

AbstractEncapsulated ferritins belong to the universally distributed ferritin superfamily, which function as iron detoxification and storage systems. Encapsulated ferritins have a distinct annular structure and must associate with an encapsulin nanocage to form a competent iron store that is capable of holding significantly more iron than classical ferritins. The catalytic mechanism of iron oxidation in the ferritin family is still an open question, due to differences in organization of the ferroxidase catalytic site and secondary metal binding sites vicinal to this. We have previously identified a metal binding site on the inner surface of the Rhodospirillum rubrum encapsulated ferritin at the interface between the two-helix subunits and proximal to the ferroxidase center. Here we present a comprehensive structural and functional study to investigate the functional relevance of this proposed iron entry site by means of enzymatic assays, mass-spectrometry, and X-ray crystallography. We show that catalysis occurs in the ferroxidase center and suggest a dual role for the secondary site, which both serves to attract metal ions to the ferroxidase center and acts as a flow-restricting valve to limit the activity of the ferroxidase center. Moreover, confinement of encapsulated ferritins within the encapsulin nanocage, while enhancing the ability of the encapsulated ferritin to undergo catalysis, does not influence the function of the secondary site.

scholarly journals Studies of the Catalytic Activity of Iron (III) Porphyrins for the Protection of Carbonyl Groups in Homogeneous Media

Catalysts ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 334 ◽  
Author(s):  
Gabriel Ferreira ◽  
Charles Carvalho ◽  
Shirley Nakagaki
Keyword(s):  
Catalytic Activity ◽  
Lewis Acids ◽  
High Reactivity ◽  
Central Metal ◽  
Carbonyl Groups ◽  
Lewis Acid Catalysts ◽  
Cyclic Acetals ◽  
Aldehydes And Ketones ◽  
Additional Coordination ◽  
Fine Chemistry

The protection of carbonyl groups that produce acetal products is a key reaction in fine chemistry due to the high reactivity of aldehydes and ketones in certain media. This process can be catalyzed by protic or Lewis acids. Since metalloporphyrins often possess free axial positions in the central metal, they can be applied as Lewis acid catalysts, allowing the additional coordination of substrates. Therefore, three ferric complexes were selected to be evaluated as catalysts for the acetalization of benzaldehyde with ethanol and triethyl orthoformate (TEOF) in the homogeneous phase: (i) 5,10,15,20-tetrakis(phenylporphyrin) iron (III) chloride (Fe0F); (ii) 5,10,15,20-tetrakis(2,6-difluorphenylporphyrin) iron (III) chloride (Fe2F); and (iii) 5,10,15,20-tetrakis(pentafluorphenylporphyrin) iron (III) chloride (Fe5F). The complex Fe5F showed the highest catalytic activity, and kinetic parameters were evaluated for this reaction, exhibiting an increasing rate of reaction of about 550-fold in comparison with the non-catalyzed reaction. The reaction scope was also investigated, and Fe5F was found to be active for the acetalization of benzaldehyde and acetophenone, with different protective agents such as alcohols, glycols, glycerol, and epoxide being selective for the formation of cyclic acetals. The protection of benzaldehyde with ethylene glycol and propylene glycol were also studied at different temperatures, and turnover frequency (TOF) values of up to 360 h−1 were determined at 40 °C in homogenous media without the need for solvent or drying agents.

The Platelet Reactivity of Collagen Type I: Evidence for Multiple Platelet-Reactive Sites in the Type I Collagen Molecule

1986 ◽  
Vol 56 (01) ◽  
pp. 095-099 ◽  
Author(s):  
C M Fitzsimmons ◽  
T E Cawston ◽  
M J Barnes
Keyword(s):  
Type I Collagen ◽  
Collagen Type ◽  
Quaternary Structure ◽  
Platelet Reactivity ◽  
Collagen Type I ◽  
Wide Distribution ◽  
Collagen Molecule ◽  
Type I ◽  
Induce Platelet Aggregation ◽  
Platelet Binding

SummaryIn this study, the ability of peptides, obtained by fragmentation of the collagen type I molecule, to induce platelet aggregation has been examined. In order to satisfy requirements for tertiary and quaternary structure, peptides were first renatured (where necessary) to restore triple-helical configuration and then polymerised. Fragmentation with mammalian collagenase indicated the presence of platelet-reactive sites in both the N-terminal three-quarter and C-terminal one quarter fragment of the collagen molecule. Cleavage with cyanogen bromide indicated the presence in the constituent cq^-chain of at least four platelet-reactive sites. Our results suggest a relatively wide distribution of platelet-binding sites situated throughout the length of the collagen (type I) molecule, each probably of relatively low affinity and low structural specificity, at least in terms of amino acid sequence, and probably of a similar nature to those that might be expected to exist in any collagen-like species.

Structural and functional insights into an archaealL-asparaginase obtained through the linker-less assembly of constituent domains

2014 ◽  
Vol 70 (12) ◽  
pp. 3187-3197 ◽  
Author(s):  
Rachana Tomar ◽  
Pankaj Sharma ◽  
Ankit Srivastava ◽  
Saurabh Bansal ◽  
Ashish ◽  
...  
Keyword(s):  
Active Site ◽  
Elevated Temperatures ◽  
Quaternary Structure ◽  
Pyrococcus Furiosus ◽  
Multidomain Proteins ◽  
Wild Type ◽  
X Ray ◽  
Data Comparison ◽  
And Function ◽  
Tetrameric Form

Covalent linkers bridging the domains of multidomain proteins are considered to be crucial for assembly and function. In this report, an exception in which the linker of a two-domain dimeric L-asparaginase fromPyrococcus furiosus(PfA) was found to be dispensable is presented. Domains of this enzyme assembled without the linker into a conjoined tetrameric form that exhibited higher activity than the parent enzyme. The global shape and quaternary structure of the conjoined PfA were also similar to the wild-type PfA, as observed by their solution scattering profiles and X-ray crystallographic data. Comparison of the crystal structures of substrate-bound and unbound enzymes revealed an altogether new active-site composition and mechanism of action. Thus, conjoined PfA is presented as a unique enzyme obtained through noncovalent, linker-less assembly of constituent domains that is stable enough to function efficiently at elevated temperatures.

The quaternary structure of E.coli inorganic pyrophosphatase is not required for catalytic activity

FEBS Letters ◽  
1985 ◽  
Vol 184 (1) ◽  
pp. 65-67 ◽  
Author(s):  
Irina B. Borschik ◽  
Tatiana V. Pestova ◽  
Vera A. Sklyankina ◽  
Svetlana M. Avaeva
Keyword(s):  
Catalytic Activity ◽  
Quaternary Structure ◽  
Inorganic Pyrophosphatase

scholarly journals Automated measurement of serum ferroxidase activity

1998 ◽  
Vol 44 (11) ◽  
pp. 2313-2319 ◽  
Author(s):  
Ozcan Erel
Keyword(s):  
Catalytic Activity ◽  
Bronchial Asthma ◽  
Copper Concentration ◽  
Acetate Buffer ◽  
Automated Measurement ◽  
Calibration System ◽  
Reaction Conditions ◽  
Serum Ceruloplasmin ◽  
Ferroxidase Activity ◽  
Healthy Persons

Abstract A method is described for automated measurement of serum ceruloplasmin ferroxidase activity. In this method, Fe2+ ions are used as the substrate. In addition, a new calibration system without ceruloplasmin is also presented. Optimum assay reaction conditions were determined. Maximal catalytic activity was obtained at 0.45 mol/L acetate buffer, pH 5.8. The reagents and calibrator are stable for at least 6 months. Significant correlations between serum ferroxidase and p-phenylenediamine oxidase activities (r = 0.96; P <0.0001) and copper concentration (r = 0.93; P <0.0001) were found. The range for serum ceruloplasmin ferroxidase activity in healthy persons was 198-1107 U/L, and in patients with bronchial asthma it was 601-1912 U/L.

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