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2000
Elisei, F, Lima JC, Ortica F, Aloisi GG, Costa M, Leitao E, Abreu I, Dias A, Bonifacio V, Medeiros J, Macanita AL, Becker RS.  2000.  Photophysical properties of hydroxy-substituted flavothiones. Journal of Physical Chemistry a. 104:6095-6102., Number 25 Abstract
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Prudencio, M, Pereira AS, Tavares P, Besson S, Cabrito I, Brown K, Samyn B, Devreese B, Van Beeumen J, Rusnak F, Fauque G, Moura JJG, Tegoni M, Cambillau C, Moura I.  2000.  Purification, characterization, and preliminary crystallographic study of copper-containing nitrous oxide reductase from Pseudomonas nautica 617. Biochemistry. {39}:{3899-3907}., Number {14} Abstract

The aerobic purification of Pseudomonas nautica 617 nitrous oxide reductase yielded two forms of the enzyme exhibiting different chromatographic behaviors. The protein contains six copper atoms per monomer, arranged in two centers named CUA and Cut. Cut could be neither oxidized nor further reduced under our experimental conditions, and exhibits a 4-line EPR spectrum (g(x)= 2.015, A(x) = 1.5 mT, g(y) = 2.071, A(y) = 2 mT, g(z) = 2.138, A(z) = 7 mT) and a strong absorption at similar to 640 nm. Cu-A can be stabilized in a reduced EPR-silent state and in an oxidized state with a typical 7-line EPR spectrum (g(x) g(y) = 2.021, A(x) = A(y) = 0 T, g(z) =0.178, A(z) = 4 mT) and absorption bands at 480, 540, and similar to 800 nm. The difference between the two purified forms of nitrous oxide reductase is interpreted as a difference in the oxidation state of the CuA center. In form A, CUA is predominantly oxidized (S = 1/2, Cu1.5+-Cu1.5+), while in form B it is mostly in the one-electron reduced state (S = 0, Cu1+-Cu1+). In both forms, Cu-Z remains reduced (S = 1/2). Complete crystallographic data at 2.4 Angstrom indicate that Cu-A is a binuclear site (similar to the site found in cytochrome c oxidase) and Cu-Z is a novel tetracopper cluster [Brown, K., et ai. (2000) Nat. Struct. Biol. (in press)]. The complete amino acid sequence of the enzyme was determined and comparisons made with sequences of other nitrous oxide reductases, emphasizing the coordination of the centers. A 10.3 kDa peptide copurified with both forms of nitrous oxide reductase shows strong homology with proteins of the heat-shock GroES chaperonin family.

1999
Alves, T, Besson S, Duarte LC, Pettigrew GW, Girio FMF, Devreese B, Vandenberghe I, Van Beeumen J, Fauque G, Moura I.  1999.  A cytochrome c peroxidase from Pseudomonas nautica 617 active at high ionic strength: expression, purification and characterization, Oct 12. Biochimica Et Biophysica Acta-Protein Structure and Molecular Enzymology. 1434:248-259., Number 2 AbstractWebsite

Cytochrome c peroxidase was expressed in cells of Pseudomonas nautica strain 617 grown under microaerophilic conditions. The 36.5 kDa dihaemic enzyme was purified to electrophoretic homogeneity in three chromatographic steps. N-terminal sequence comparison showed that the Ps. nautica enzyme exhibits a high similarity with the corresponding proteins from Paracoccus denitrificans and Pseudomonas aeruginosa. UV-visible spectra confirm calcium activation of the enzyme through spin state transition of the peroxidatic haem. Monohaemic cytochrome c(552) from Ps. nautica was identified as the physiological electron donor, with a half-saturating concentration of 122 mu M and allowing a maximal catalytic centre activity of 116 000 min(-1). Using this cytochrome the enzyme retained the same activity even at high ionic strength. There are indications that the interactions between the two redox partners are mainly hydrophobic in nature. (C) 1999 Elsevier Science B.V. All rights reserved.

Dias, JM, Than ME, Humm A, Huber R, Bourenkov GP, Bartunik HD, Bursakov S, Calvete J, Caldeira J, Carneiro C, Moura JJ, Moura I, Romao MJ.  1999.  Crystal structure of the first dissimilatory nitrate reductase at 1.9 A solved by MAD methods, Jan 15. Structure. 7:65-79., Number 1 AbstractWebsite

BACKGROUND: The periplasmic nitrate reductase (NAP) from the sulphate reducing bacterium Desulfovibrio desulfuricans ATCC 27774 is induced by growth on nitrate and catalyses the reduction of nitrate to nitrite for respiration. NAP is a molybdenum-containing enzyme with one bis-molybdopterin guanine dinucleotide (MGD) cofactor and one [4Fe-4S] cluster in a single polypeptide chain of 723 amino acid residues. To date, there is no crystal structure of a nitrate reductase. RESULTS: The first crystal structure of a dissimilatory (respiratory) nitrate reductase was determined at 1.9 A resolution by multiwavelength anomalous diffraction (MAD) methods. The structure is folded into four domains with an alpha/beta-type topology and all four domains are involved in cofactor binding. The [4Fe-4S] centre is located near the periphery of the molecule, whereas the MGD cofactor extends across the interior of the molecule interacting with residues from all four domains. The molybdenum atom is located at the bottom of a 15 A deep crevice, and is positioned 12 A from the [4Fe-4S] cluster. The structure of NAP reveals the details of the catalytic molybdenum site, which is coordinated to two MGD cofactors, Cys140, and a water/hydroxo ligand. A facile electron-transfer pathway through bonds connects the molybdenum and the [4Fe-4S] cluster. CONCLUSIONS: The polypeptide fold of NAP and the arrangement of the cofactors is related to that of Escherichia coli formate dehydrogenase (FDH) and distantly resembles dimethylsulphoxide reductase. The close structural homology of NAP and FDH shows how small changes in the vicinity of the molybdenum catalytic site are sufficient for the substrate specificity.

Almendra, MJ, Brondino CD, Gavel O, Pereira AS, Tavares P, Bursakov S, Duarte R, Caldeira J, Moura JJ, Moura I.  1999.  Purification and characterization of a tungsten-containing formate dehydrogenase from Desulfovibrio gigas, Dec 7. Biochemistry. 38:16366-72., Number 49 AbstractWebsite

An air-stable formate dehydrogenase (FDH), an enzyme that catalyzes the oxidation of formate to carbon dioxide, was purified from the sulfate reducing organism Desulfovibrio gigas (D. gigas) NCIB 9332. D. gigas FDH is a heterodimeric protein [alpha (92 kDa) and beta (29 kDa) subunits] and contains 7 +/- 1 Fe/protein and 0.9 +/- 0.1 W/protein. Selenium was not detected. The UV/visible absorption spectrum of D. gigas FDH is typical of an iron-sulfur protein. Analysis of pterin nucleotides yielded a content of 1.3 +/- 0.1 guanine monophosphate/mol of enzyme, which suggests a tungsten coordination with two molybdopterin guanine dinucleotide cofactors. Both Mossbauer spectroscopy performed on D. gigas FDH grown in a medium enriched with (57)Fe and EPR studies performed in the native and fully reduced state of the protein confirmed the presence of two [4Fe-4S] clusters. Variable-temperature EPR studies showed the presence of two signals compatible with an atom in a d(1) configuration albeit with an unusual relaxation behavior as compared to the one generally observed for W(V) ions.

Dias, JM, Bursakov S, Carneiro C, Moura JJ, Moura I, Romao MJ.  1999.  Crystallization and preliminary x-ray analysis of a nitrate reductase from Desulfovibrio desulfuricans ATCC 27774, Apr. Acta Crystallogr D Biol Crystallogr. 55:877-9., Number Pt 4 AbstractWebsite

Periplasmic nitrate reductase from the sulfate-reducing bacterium Desulfovibrio desulfuricans ATCC 27774 contains two molybdopterin guanine dinucleotide cofactors and one [4Fe-4S] cluster as prosthetic groups and catalyzes the conversion of nitrate to nitrite. Crystals of the oxidized form of this enzyme were obtained using PEG as precipitant and belong to space group P3121 or P3221, with unit-cell dimensions a = b = 106.3, c = 135.1 A. There is one monomer of 80 kDa in the asymmetric unit, which corresponds to a Matthews ratio of 2.75 A3 Da-1. Using cryo-cooling procedures and X-rays from a rotating-anode generator, diffraction was observed to beyond 3.0 A resolution.

Bursakov, SA, Brondino C, Dias JM, Carneiro C, Caldeira J, Duarte RO, Romao MJ, Moura I, Moura JJG.  1999.  Cross immunological reactions and spectroscopy study within nitrate reductase and other mononuclear Mo containing enzymes of the sulfate reducing bacteria. Journal of Inorganic Biochemistry. 74:86-86., Number 1-4 AbstractWebsite
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Dias, JM, Than ME, Humm A, Huber R, Bourenkov GP, Bartunik HD, Bursakov S, Calvete J, Caldeira J, Carneiro C, Moura JJG, Moura I, Romao MJ.  1999.  Crystal structure of the first dissimilatory nitrate reductase at 1.9 angstrom solved by MAD methods. Structure with Folding & Design. 7:65-79., Number 1 AbstractWebsite
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Dias, JM, Bursakov S, Carneiro C, Moura JJG, Moura I, Romao MJ.  1999.  Crystallization and preliminary X-ray analysis of a nitrate reductase from Desulfovibrio desulfuricans ATCC 27774. Acta Crystallographica Section D-Biological Crystallography. 55:877-879. AbstractWebsite
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Dias, JM, Than ME, Huber R, Bourenkov GP, Bartunik HD, Bursakov S, Moura JJG, Moura I, Romao MJ.  1999.  Crystallographic studies of a dissimilatory nitrate reductase and mechanistic implications. Journal of Inorganic Biochemistry. 74:113-113., Number 1-4 AbstractWebsite
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Teixeira, S, Dias JM, Carvalho AL, Bourenkov G, Bartunik H, Almendra MJ, Moura I, Moura JJG, Romao MJ.  1999.  Crystallographic studies on a tungsten-containning formate dehydrogenase from Desulfovibrio gigas. Journal of Inorganic Biochemistry. 74:89-89., Number 1-4 AbstractWebsite
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Romao, MJ, Carvalho AL, Dias JM, Teixeira S, Bourenkov G, Bartunik H, Huber R, Maia L, Mira L.  1999.  Preliminary crystallographic studies of xanthine oxidase purified from rat liver. Journal of Inorganic Biochemistry. 74:281-281., Number 1-4 AbstractWebsite
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Almendra, MJ, Brondino CD, Gavel O, Pereira AS, Tavares P, Bursakov S, Duarte R, Caldeira J, Moura JJG, Moura I.  1999.  Purification and characterization of a tungsten-containing formate dehydrogenase from Desulfovibrio gigas. Biochemistry. {38}:{16366-16372}., Number {49} Abstract

An air-stable formate dehydrogenase (FDH), an enzyme that catalyzes the oxidation of formate to carbon dioxide, was purified from the sulfate reducing organism Desulfovibrio gigas (D. gigas) NCIB 9332. D. gigas FDH is a heterodimeric protein [alpha (92 kDa) and beta (29 kDa) subunits] and contains 7 +/- 1 Fe/protein and 0.9 +/- 0.1 W/protein, Selenium was not detected. The UV/visible absorption spectrum of D, gigas FDH is typical of an iron-sulfur protein. Analysis of pterin nucleotides yielded a content of 1.3 +/- 0.1 guanine monophosphate/mol of enzyme, which suggests a tungsten coordination with two molybdopterin guanine dinucleotide cofactors. Both Mossbauer spectroscopy performed on D. gigas FDH grown in a medium enriched with Fe-57 and EPR studies performed in the native and fully reduced state of the protein confirmed the presence of two [4Fe-4S] clusters. Variable-temperature EPR studies showed the presence of two signals compatible with an atom in a d(1) configuration albeit with an unusual relaxation behavior as compared to the one generally observed for W(V) ions.

1998
Pettigrew, GW, Gilmour R, Goodhew CF, Hunter DJ, Devreese B, Van Beeumen J, Costa C, Prazeres S, Krippahl L, Palma PN, Moura I, Moura JJ.  1998.  The surface-charge asymmetry and dimerisation of cytochrome c550 from Paracoccus denitrificans--implications for the interaction with cytochrome c peroxidase, Dec 1. Eur J Biochem. 258:559-66., Number 2 AbstractWebsite

The implications of the dimeric state of cytochrome c550 for its binding to Paracoccus cytochrome c peroxidase and its delivery of the two electrons required to restore the active enzyme during catalysis have been investigated. The amino acid sequence of cytochrome c550 of Paracoccus denitrificans strain LMD 52.44 was determined and showed 21 differences from that of strain LMD 22.21. Based on the X-ray structure of the latter, a structure for the cytochrome c550 monomer from strain 52.44 is proposed and a dipole moment of 945 debye was calculated with an orientation close to the exposed haem edge. The behaviour of the cytochrome on molecular-exclusion chromatography is indicative of an ionic strength-dependent monomer (15 kDa)/dimer (30 kDa) equilibrium that can also be detected by 1H-NMR spectroscopy. The apparent mass of 50 kDa observed at very low ionic strength was consistent with the presence of a strongly asymmetric dimer. This was confirmed by cross-linking studies, which showed that a cross-linked species of mass 30 kDa on SDS behaved with an apparent mass of 50 kDa on molecular-exclusion chromatography. A programme which carried out and evaluated molecular docking of two monomers to give a dimer generated a most probable dimer in which the monomer dipoles lay almost antiparallel to each other. The resultant dipole moment of the dimer is therefore small. Although this finding calls into question the possibility of preorientation of a strongly asymmetrically charged cytochrome as it collides with a redox partner, the stoichiometry of complex formation with cytochrome c peroxidase as studied by 1H-NMR spectroscopy shows that it is the monomer that binds.

Goodfellow, BJ, Rusnak F, Moura I, Domke T, Moura JJ.  1998.  NMR determination of the global structure of the 113Cd derivative of desulforedoxin: investigation of the hydrogen bonding pattern at the metal center, Apr. Protein Sci. 7:928-37., Number 4 AbstractWebsite

Desulforedoxin (Dx) is a simple homodimeric protein isolated from Desulfovibrio gigas (Dg) containing a distorted rubredoxin-like center with one iron coordinated by four cysteinyl residues (7.9 kDa with 36 amino acids per monomer). In order to probe the geometry and the H-bonding at the active site of Dx, the protein was reconstituted with 113Cd and the solution structure determined using 2D NMR methods. The structure of this derivative was initially compared with the NMR solution structure of the Zn form (Goodfellow BJ et al., 1996, J Biol Inorg Chem 1:341-353). Backbone amide protons for G4, D5, G13, L11 NH, and the Q14 NH side-chain protons, H-bonded in the X-ray structure, were readily exchanged with solvent. Chemical shift differences observed for amide protons near the metal center confirm the H-bonding pattern seen in the X-ray model (Archer M et al., 1995, J Mol Biol 251:690-702) and also suggest that H-bond lengths may vary between the Fe, Zn, and 113Cd forms. The H-bonding pattern was further probed using a heteronuclear spin echo difference (HSED) experiment; the results confirm the presence of NH-S H-bonds inferred from D2O exchange data and observed in the NMR family of structures. The presence of "H-bond mediated" coupling in Dx indicates that the NH-S H-bonds at the metal center have significant covalent character. The HSED experiment also identified an intermonomer "through space" coupling for one of the L26 methyl groups, indicating its proximity to the 113Cd center in the opposing monomer. This is the first example of an intermonomer "through space" coupling. Initial structure calculations produced subsets of NMR families with the S of C28 pointing away from or toward the L26 methyl: only the subset with the C28 sulfur pointing toward the L26 methyl could result in a "through space" coupling. The HSED result was therefore included in the structure calculations. Comparison of the Fe, Zn, and 113Cd forms of Dx suggests that the geometry of the metal center and the global fold of the protein does not vary to any great extent, although the H-bond network varies slightly when Cd is introduced. The similarity between the H-bonding pattern seen at the metal center in Dx, Rd (including H-bonded and through space-mediated coupling), and many zinc-finger proteins suggests that these H-bonds are structurally vital for stabilization of the metal centers in these proteins.

Saraiva, LM, Salgueiro CA, da Costa PN, Messias AC, Legall J, van Dongen WMAM, Xavier AV.  1998.  Replacement of Lysine 45 by Uncharged Residues Modulates the Redox-Bohr Effect in Tetraheme Cytochrome c3 of Desulfovibrio vulgaris (Hildenborough). Biochemistry. 37(35):12160-12165. AbstractWebsite

The structural basis for the pH dependence of the redox potential in the tetrahemic Desulfovibrio vulgaris (Hildenborough) cytochrome c3 was investigated by site-directed mutagenesis of charged residues in the vicinity of heme I. Mutation of lysine 45, located in the neighborhood of the propionates of heme I, by uncharged residues, namely threonine, glutamine and leucine, was performed. The replacement of a conserved charged residue, aspartate 7, present in the N-terminal region and near heme I was also attempted. The analysis of the redox interactions as well as the redox-Bohr behavior of the mutated cytochromes c3 allowed the conclusion that residue 45 has a functional role in the control of the pKa of the propionate groups of heme I and confirms the involvement of this residue in the redox-Bohr effect.

Valentine, AM, Tavares P, Pereira AS, Davydov R, Krebs C, Koffman BM, Edmondson DE, Huynh BH, Lippard SJ.  1998.  Generation of a mixed-valent Fe(III)Fe(IV) form of intermediate Q in the reaction cycle of soluble methane monooxygenase, an analog of intermediate X in ribonucleotide reductase R2 assembly. Journal Of The American Chemical Society. {120}:{2190-2191}., Number {9} Abstract
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Stalhandske, CMV, Dong J, Tavares P, Liu MY, Legall J, Moura JJG, Moura I, Park JB, Adams MWW, Scott RA.  1998.  Probing the iron environment in desulforedoxin. EXAFS of oxidized and reduced states. INORGANICA CHIMICA ACTA. {273}:{409-411}., Number {1-2} Abstract

Fe XAS data were collected on the oxidized and reduced forms of desulforedoxin from Desulfovibrio gigas, the oxidized form of rubredoxin from Clostridium pasteurianum, and the reduced form of rubredoxin from Pyrococcus furiosus. Analysis of these data is consistent with tetrahedral FeS(4) coordination in both oxidation states, and an expansion of the Fe-S distances from 2.27 to 2.33 Angstrom upon reduction. (C) 1998 Elsevier Science S.A. All rights reserved.

1997
Devreese, B, Costa C, Demol H, Papaefthymiou V, Moura I, Moura JJ, Van Beeumen J.  1997.  The primary structure of the split-Soret cytochrome c from Desulfovibrio desulfuricans ATCC 27774 reveals an unusual type of diheme cytochrome c, Sep 1. Eur J Biochem. 248:445-51., Number 2 AbstractWebsite

The complete amino acid sequence of the unusual diheme split-Soret cytochrome c from the sulphate-reducing Desulfovibrio desulfuricans strain ATCC 27774 has been determined using classical chemical sequencing techniques and mass spectrometry. The 247-residue sequence shows almost no similarity with any other known diheme cytochrome c, but the heme-binding site of the protein is similar to that of the cytochromes c3 from the sulphate reducers. The cytochrome-c-like domain of the protein covers only the C-terminal part of the molecule, and there is evidence for at least one more domain containing four cysteine residues, which might bind another cofactor, possibly a non-heme iron-containing cluster. This domain is similar to a sequence fragment of the genome of Archaeoglobus fulgidus, which confirms the high conservation of the genes involved in sulfate reduction.

Bursakov, SA, Carneiro C, Almendra MJ, Duarte RO, Caldeira J, Moura I, Moura JJ.  1997.  Enzymatic properties and effect of ionic strength on periplasmic nitrate reductase (NAP) from Desulfovibrio desulfuricans ATCC 27774, Oct 29. Biochem Biophys Res Commun. 239:816-22., Number 3 AbstractWebsite

Some sulfate reducing bacteria can induce nitrate reductase when grown on nitrate containing media being involved in dissimilatory reduction of nitrate, an important step of the nitrogen cycle. Previously, it was reported the purification of the first soluble nitrate reductase from a sulfate-reducing bacteria Desulfovibrio desulfuricans ATCC 27774 (S.A. Bursakov, M.-Y. Liu, W.J. Payne, J. LeGall, I. Moura, and J.J.G. Moura (1995) Anaerobe 1, 55-60). The present work provides further information about this monomeric periplasmic nitrate reductase (Dd NAP). It has a molecular mass of 74 kDa, 18.6 U specific activity, KM (nitrate) = 32 microM and a pHopt in the range 8-9.5. Dd NAP has peculiar properties relatively to ionic strength and cation/anion activity responses. It is shown that monovalent cations (potassium and sodium) stimulate NAP activity and divalent (magnesium and calcium) inhibited it. Sulfate anion also acts as an activator in KPB buffer. NAP native form is protected by phosphate anion from cyanide inactivation. In the presence of phosphate, cyanide even stimulates NAP activity (up to 15 mM). This effect was used in the purification procedure to differentiate between nitrate and nitrite reductase activities, since the later is effectively blocked by cyanide. Ferricyanide has an inhibitory effect at concentrations higher than 1 mM. The N-terminal amino acid sequence has a cysteine motive C-X2-C-X3-C that is most probably involved in the coordination of the [4Fe-4S] center detected by EPR spectroscopy. The active site of the enzyme consists in a molybdopterin, which is capable for the activation of apo-nit-1 nitrate reductase of Neurospora crassa. The oxidized product of the pterin cofactor obtained by acidic hidrolysis of native NAP with sulfuric acid was identified by HPLC chromatography and characterized as a molybdopterin guanine dinucleotide (MGD).

Duarte, RO, Reis AR, Girio F, Moura I, Moura JJ, Collaco TA.  1997.  The formate dehydrogenase isolated from the aerobe Methylobacterium sp. RXM is a molybdenum-containing protein, Jan 3. Biochem Biophys Res Commun. 230:30-4., Number 1 AbstractWebsite

The formate dehydrogenase (FDH) isolated from cells of Methylobacterium sp. RXM grown on molybdenum-containing mineral medium using methanol as carbon source, was partially purified (at least 90% pure as revealed by SDS-PAGE). The enzyme is unstable under oxygen and all the purification steps were conducted under strict anaerobic conditions. The molecular mass is 75 kDa (gel exclusion 300 kDa). The enzyme was characterized in terms of the kinetic parameters towards different substrates and electron acceptors, pH and temperature dependence and the effect of a wide range of compounds in the enzymatic activity. The EPR spectra of the dithionite reduced sample show, at low temperature (below 20 K), two rhombic EPR signals due to two distinct [Fe-S] centres (centre I at g-values 2.023, 1.951 and 1.933, and centre II at g-values 2.054 and 1.913). At high temperature (around 100 K) another rhombic EPR signal is optimally observed at g-values 2.002, 1.987 and 1.959 and attributed to the molybdenum site. The EPR signals assigned to the iron-sulfur centres show a strong analogy with the aldehyde oxido-reductase from Desulfovibrio gigas known to contain a Mo-pterin and two [2Fe-2S] centres and whose crystallographic structure was recently resolved.

Romao, MJ, Kolln I, Dias JM, Carvalho AL, Romero A, Varela PF, Sanz L, Topfer-Petersen E, Calvete JJ.  1997.  Crystal structure of acidic seminal fluid protein (aSFP) at 1.9 angstrom resolution: a bovine polypeptide of the spermadhesin family. Journal of Molecular Biology. 274:650-660., Number 4 AbstractWebsite
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Archer, M, Banci L, Dikaya E, Romao MJ.  1997.  Crystal structure of cytochrome c' from Rhodocyclus gelatinosus and comparison with other cytochromes c'. Journal of Biological Inorganic Chemistry. 2:611-622., Number 5 AbstractWebsite
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Romero, A, Romao MJ, Varela PF, Kolln I, Dias JM, Carvalho AL, Sanz L, TopferPetersen E, Calvete JJ.  1997.  The crystal structures of two spermadhesins reveal the CUB domain fold. Nature Structural Biology. 4:783-788., Number 10 AbstractWebsite
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