Evolutionary relationships between heme-binding ferredoxin α + β barrels
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The α + β barrel superfamily of the ferredoxin-like fold consists of a functionally diverse group of evolutionarily related proteins. The barrel architecture of these proteins is formed by either homo-/hetero-dimerization or duplication and fusion of ferredoxin-like domains. Several members of this superfamily bind heme in order to carry out their functions.
We analyze the heme-binding sites in these proteins as well as their barrel topologies. Our comparative structural analysis of these heme-binding barrels reveals two distinct modes of packing of the ferredoxin-like domains to constitute the α + β barrel, which is typified by the Type-1/IsdG-like and Type-2/OxdA-like proteins, respectively. We examine the heme-binding pockets and explore the versatility of the α + β barrels ability to accommodate heme or heme-related moieties, such as siroheme, in at least three different sites, namely, the mode seen in IsdG/OxdA, Cld/DyP/EfeB/HemQ and siroheme decarboxylase barrels.
Our study offers insights into the plausible evolutionary relationships between the two distinct barrel packing topologies and relate the observed heme-binding sites to these topologies.
KeywordsHemoprotein Barrel packing Heme Iron metabolism Protein evolution
antibiotic biosynthesis monooxygenases
Cld DyP EfeB
fold and function assignment system
multiple sequence alignment
Profile Consistency Multiple Sequence Alignment
protein data bank
position-specific iterative basic local alignment search tool
structural classification of proteins
The “dimeric α + β barrel superfamily” (Pfam CL0032, SCOP identifier 54909) is an evolutionarily conserved group of protein families found in all three kingdoms of life [1, 2, 3, 4]. Proteins of this superfamily include the antibiotic biosynthesis monooxygenases (ABM; PF03992) , transcription regulators of the AsnC family (PF01037) , polyketide synthases (PF04673) , ether compound degraders (PF07110) , etc. Some families of this superfamily are involved in degradation and synthesis of heme (Iron-regulated surface determinants, IsdG and IsdI, which are members of the ABM family and HemQ, respectively) [9, 10]. This superfamily is also referred to as the CDE superfamily in literature, CDE being an acronym for the chlorite dismutase (Cld, PF06778), dye-decolorizing peroxidase (DyP, PF04261) and EfeB heme-binding families [2, 11].
The proteins of this superfamily are made up of two domains that pack together as a closed barrel (SCOP identifier 54909) (Fig. 1a). Each domain has a ferredoxin-like fold (SCOP identifier 54861) with two repeats of a β-α-β structural motif that form a two-layer α + β sandwich (β1-α1-β2-β3-α2-β4) with an antiparallel β-sheet. The antiparallel β-sheet from two such ferredoxin-like domains interact and form a barrel with an all β layer on the inside decorated with α-helices on the outside (Fig. 1a). The two ferredoxin-like domains involved in barrel formation may be present as tandemly duplicated and fused domains on a single polypeptide chain or as standalone domains from separate protein chains. Based on the initially determined structures, this superfamily was named the “dimeric alpha + beta barrel ” by SCOP (v1.63) as two ferredoxin-like domains were seen to dimerize to form the barrel and this terminology has been used extensively in the literature. However, this nomenclature is a misnomer as many structures with two ferredoxin-like domains from a single polypeptide that adopts a barrel architecture are now available. Thus, in order to avoid confusion, we refer to this superfamily as the ferredoxin α + β barrel and suggest the adoption of this nomenclature for this superfamily. Further, the ferredoxin-like domains from different chains may form a barrel by combining with identical domains (homodimers) or evolutionarily related domains (heterodimers). For example, in most IsdG homologs a single ferredoxin-like domain is present per protein chain which homodimerizes to form the barrel [17, 26, 27] (Fig. 1), while in most members of the Cld, Dyp, EfeB, HemQ and OxdA families, two duplicated and fused ferredoxin-like domains are present in tandem on the same polypeptide to form the barrel [12, 14, 22, 28, 29]. In several of the ferredoxin α + β barrel families, biologically significant higher oligomeric forms are observed [2, 12, 14, 28, 29]. For example, proteins of the DyP, Cld, EfeB, HemQ and OxdA families are known to contain dimeric, trimeric, pentameric and hexameric copies of the ferredoxin α + β barrel [12, 14, 28, 29], and proteins of the muconolactone isomerase family and sulphur oxygenase reductase are known to exist as homo decamer and an oligomer made of 24 barrel units, respectively [30, 31].
While many studies describing the structural and biochemical characterization of these proteins are available, an evolutionary basis for the emergence of different heme-binding sites in the ferredoxin α + β barrel and rationale for the apparently different barrel packing is not available. Here, we present a comparative view of the different heme-binding ferredoxin α + β barrel families based on evolutionary considerations and identify two different barrel packing modes of the ferredoxin-like domains. The evolutionary scenarios that likely resulted in the topologically different packing modes are discussed. Further, we provide a comparative topological- and structural view of the various heme-binding sites in the versatile ferredoxin α + β barrel. It is particularly interesting to observe how the ferredoxin-like protein domain has evolved to utilize different interfaces for performing varied functions around the heme moiety. This work could be potentially useful for future protein structural and evolutionary studies and in understanding the spatial packing of protein domains.
Results and discussion
Barrel packing topologies observed in heme-binding members of the ferredoxin α + β barrel superfamily
Arrangement of ferredoxin-like domains in the barrels
Heme-binding ferredoxin α + β barrel family representatives
β-strand of the ferredoxin-like domain involved in barrel packing
IsdG and IsdI-like (PDB identifiers 2ZDO, 2ZDP, 3LGM, 3LGN, 3QGP, 4FNH, 4FNI)
MhuD (PDB identifiers 3HX9, 4NL5)
Siroheme decarboxylase (PDB identifier 4UN1)
Dimerization of tandemly duplicated and fused domains
HmoB (PDB identifiers 4FVC, 4JOU, 4OZ5), Chlorite dismutase (PDB identifiers 2VXH, 3NN1, 3NN2, 3NN3, 3NN4, 3Q08, 3Q09, 3QPI, 4 M05, 4 M06, 4 M07, 4 M08, 4 M09), Dyp-type peroxidase (PDB identifier 2D3Q, 2IIZ 3AFV, 3MM1, 3MM2, 3MM3, 3QNR, 3QNS, 3VEC, 3VED, 3VEF, 3VEG, 3VXI, 3VXJ, 4 AU9, 4G2C, 4GRC, 4GS1, 4GT2, 4GU7, 4HOV, 4UZI, 4W7J, 4W7K, 4W7L, 4W7M, 4W7N, 4W7O), EfeB (PDB identifiers 2Y4E, 2Y4F, 3O72), Siroheme decarboxylase (PDB identifier 4CZC)
Aldoxime dehydratase (PDB identifiers 3A15, 3A16, 3A17, 3A18, 3 W08)
Detailed comparison of different heme-/siroheme-binding ferredoxin α + β barrel families
Number of heme/siroheme per barrel
2 (IsdG/IsdI, PDB identifier 2ZDO/2ZDP) (1/monomer)
1 (in C-terminal ferredoxin-like domain)
1 (between the two ferredoxin-like domains)
4 (MhuD, PDB identifier 3HX9) (2/monomer)
1 (HmoB, PDB identifier 4OZ5) (1 in C-terminal ferredoxin-like domain)
Heme/siroheme binding pocket
Cleft of the ferredoxin-like domain
Function of heme/siroheme
Cofactor, Product (HemQ)
Shape of heme/siroheme
Location of the proximal His-axial residue
α2 of ferredoxin-like domain (α3 in the contiguous duplicated domains in HmoB)
α2 of the ferredoxin-like domain (α4 in the contiguous duplicated domains). These are spatially not equivalent to α2 of IsdG homologs.
α1 of the ferredoxin-like domain (α3 in the contiguous duplicated domains). These are spatially equivalent to OxdA.
β2 of the ferredoxin-like domain of chain A in D. desulfuricans. β6 of the contiguous duplicated domains of the barrel in H. thermophilus
Distal heme residue
The second heme-binding site, structurally distinct from IsdG and OxdA , is seen in Cld/DyP/EfeB/HemQ proteins, where the heme-binding histidine though contributed by the C-terminal domain, is located on α3 of the barrel. Further, α3 of Cld/DyP/EfeB/HemQ barrels is also topologically equivalent to the α1 of the ferredoxin-like domain of IsdG, similar to the OxdA proteins (Table 2, Fig. 2d, f), which allows us to relate the C-terminal domains of OxdA and Cld/DyP/EfeB/HemQ barrels by a circular permutation. Hence, by considering, first, a 1800 rotation of the C-terminal domain in OxdA with respect to the domain of IsdG, and second, a circular permutation in the heme-binding domain of Cld/DyP/EfeB/HemQ proteins relative to that of OxdA, we were able to align the heme-binding site in the IsdG ferredoxin-like monomer (PDB identifier 2ZDP), and the C-terminal domains of the OxdA (PDB identifier 3A16_A) and the Cld/DyP/EfeB/HemQ (PDB identifier 3NN1_A) barrels (Fig. 3a). The IsdG ferredoxin-like monomer (PDB identifier 2ZDP) and 1800-rotated C-terminal domain of OxdA (PDB identifier 3A16) could be manual superimposed with an RMSD of 1.16 Å over 50 pairs of Cα-atoms, while the C-terminal domain of OxdA (PDB identifier 3A16) and Cld (PDB identifier 3NN1) could be superimposed with an RMSD of 2.63 Å over 53 pairs of Cα-atoms.
Homologs of IsdG, OxdA, and Cld/DyP/EfeB/HemQ were obtained by sequence similarity searches initiated using JackHMMER . A multiple sequence alignment (MSA) of IsdG, the C-terminal domains of OxdA and the C-terminal domains of Cld/DyP/EfeB/HemQ members is presented in Fig. 3c. As shown in the MSA, the exact location of the heme-binding histidine (highlighted black in Fig. 3c) is variable among members of the ferredoxin α + β barrel proteins. MSA of the structurally characterized IsdG and OxdA proteins reveal that the histidine is present at non-identical positions in the ferredoxin-like domain, i.e. histidine in OxdA proteins is three residues away from the histidine in IsdG. Structurally, this implies that the heme-binding histidine in OxdA is one α-helical-turn before the histidine of IsdG (Fig. 3a). However, we could find several sequences of the IsdG family (UniProt ID: F6IIL5, D6U1Z7 in Fig. 3c) which also possess a histidine at an equivalent position to OxdA (highlighted in magenta in Fig. 3c), suggesting a possible migration of heme-binding site in these evolutionarily related ferredoxin-like domains. In some of the IsdG proteins (UniProt ID: E7FTP1, G5JP20 in Fig. 3c), two histidines are present, one of which is at the position seen in IsdGs and the other at the position corresponding to that of OxdA heme-binding histidine. Besides the conservation of the pattern of histidines, we observe conservation of several hydrophobic (highlighted in gray in Fig. 3c) and aromatic residues (highlighted in cyan in Fig. 3c) which is indicative of an evolutionary relation among the IsdG and OxdA proteins and consequently, their heme-binding sites. Further, automated sequence similarity searches using FFAS , initiated with the full-length OxdA proteins could find high-scoring matches to members of the ABM/IsdG family, but not to other members of the Pfam “dimeric α + β barrel” clan (CL0032). For example, OxdA (PDB identifier 3A16, residues 6–367) could find IsdI (PDB identifier 2ZDP_A, Score = −14.1), Antibiotic biosynthesis monooxygenase (PDB identifier 2RIL_A, Score = −13.6) and YqjZ (PDB identifier 2G08_A, Score = −13.5) as the top scoring matches in searches initiated against the PDB database. An FFAS score lower than −9.5 is associated with < 3 % false positive hits and higher confidence may be vested with hits with scores lower than this . Statistically significant sequence similarity is used as a measure of homology  and these scores reveal a rather close relation between the OxdA and IsdG/ABM-family members as compared to other families of the ferredoxin α + β barrel.
A plausible evolutionary scenario that could have led to the emergence of different packing modes and heme-binding sites is detailed below. However, from a structural viewpoint as both the ferredoxin-like domain packing modes lead to formation of a similar barrel, thus, any apparent reason for one type being favored over the other during evolution is not evident. The simplest manner in which a α + β barrel could have emerged is by homodimerization of identical ferredoxin-like domains. The ferredoxin-like domains could have packed in two non-identical modes (similar to Type-1 in IsdG and Type-2 in YqjZ, PDB identifier 2ZDO and 2GO8, respectively). Further, duplication and divergence would have likely resulted in non-identical ferredoxin-like domains that could heterodimerize. The heterodimerization could also be of either type, but the structure for only the Type-1 packing mode is known currently (as seen in siroheme decarboxylase, PDB identifier 4UN1). Likewise, a tandem duplication and fusion of the ferredoxin-like domains would have resulted in a barrel formed from two domains present on a single polypeptide. However, these could again pack in the two aforementioned modes dictated possibly by the flexibility of the linker region between the domains (similar to Type-1 in HmoB and Type-2 in OxdA, PDB identifiers 4OZ5 and 3A16, respectively). The presence of tandemly duplicated ferredoxin-like domains is likely to have eased the evolutionary pressure for heme binding on both the domains and thus, only one domain retained the heme-binding histidine (mostly the C-terminal domain as seen in HmoB, Cld, DyP, EfeB, OxdA). The N-terminal domain, thereafter, likely served a mere structural role in barrel packing and is even seen to have lost some of the secondary structural elements of the ferredoxin α + β barrel scaffold, for example in the HmoB protein. The structure of HmoB (PDB identifiers 3TVZ, 4FVC, 4JOU, 4OZ5) reveals the degradation of the α-helix, equivalent to the heme-binding α-helix of the ferredoxin-like domain of evolutionary-related IsdG proteins, in its N-terminal domain (Fig. 2). Further, although the Cld/DyP/EfeB/HemQ barrels have a Type-1 packing similar to that seen in IsdG, their heme-binding histidine is on an α-helix which is topologically equivalent to that of OxdA Type-2-packed barrel (Fig. 2), thus allowing us to relate the C-terminal domains of OxdA and Cld/DyP/EfeB/HemQ by a probable circular permutation event. Nonetheless, the possibility of having acquired heme-binding ability independent of other ferredoxin α + β barrels cannot be ruled out. Interestingly, initial structural studies of the DyP family proteins attributed the presence of heme at two different positions [39-41], but subsequent studies established a single heme-binding site in DyP proteins based on conservation of one of the proximal histidine [13, 21]. Further, in another study concerning the structural characterization of HmoB from B. subtilis (PDB identifier 4FVC_A), heme is seen to bind to a nearby Tyr residue (boxed in red in Fig. 3c) when the secondary structure element with the proximal histidine is disordered. Intriguingly, the position of this Tyr residue is equivalent to the heme-binding histidine in OxdA, thus providing additional evidence in favor of evolutionary relatedness of IsdG and OxdA families and migration of the heme-binding site. Thus, these examples together with the analysis of heme-binding barrels reveal the versatility of the ferredoxin-like domain to accommodate heme at different locations.
A vivid example of the independent emergence of heme-like-moiety-binding is that of siroheme decarboxylase, an enzyme of the alternative heme synthesis pathway which catalyzes the conversion of siroheme to 12, 18 didecarboxysiroheme [23, 24, 25]. Evidence in favor of independent acquisition of siroheme-binding in siroheme decarboxylase include, firstly, that siroheme binds at a completely different region, i.e. inside the barrel cavity, as compared to other ferredoxin α + β barrel proteins which bind heme within the cleft of the ferredoxin-like domain (Figs. 1a and 3b, Table 2) and secondly, their probable homologous relation to proteins of the AsnC family  which are known to primarily function in transcription regulation pathways [2, 43]. The sequences of the ferredoxin-like domains of siroheme decarboxylase (PDB identifiers 4UN1, 4CZC) are not currently classified in Pfam but find high-scoring matches to AsnC family proteins using PSI-BLAST. For example, H. thermophilus siroheme decarboxylase (PDB identifier 4CZC_A) finds matches to uncharacterized HTH-type transcriptional regulator PH1519 (UniProt identifier O59188, with an E-value 3e-06) and uncharacterized HTH-type transcriptional regulator PYRAB06490 (UniProt identifier Q9V0Y9, with an E-value of 3e-05).
We refer to the mode of siroheme-binding in siroheme decarboxylase (PDB identifiers 4UN1, 4CZC) as the third mode of heme binding observed in ferredoxin α + β barrel families, as unlike the aforementioned families which bind heme in the cleft of the ferredoxin-like domain, siroheme decarboxylase binds siroheme in the barrel cavity formed by the two ferredoxin-like domains (Fig. 1a). The histidine which binds siroheme is located on a β-strand of the ferredoxin-like domain and not on a α-helix like the other heme-binding α + β barrels (Fig. 2e). Thus, this mode of heme binding cannot be related to the IsdG, Cld/DyP/EfeB/HemQ and OxdA by any of the evolutionary mechanisms discussed above, such as circular permutation, rotation of the ferredoxin-like domains, etc. Interestingly, though the two structurally characterized siroheme decarboxylases (PDB identifiers 4UN1, 4CZC) possess a similar barrel cavity as the site for siroheme-binding, the siroheme moiety is bound and oriented differently in these proteins. While the heme-binding histidine is located at the same position, i.e. on the β2 strand, the barrel reveals that the histidine is contributed by β2 of chain A in D. desulfuricans (PDB identifier 4UN1) and from β6 of the barrel of H. thermophilus (PDB identifier 4CZC). H. thermophilus siroheme decarboxylase (PDB identifier 4CZC) as mentioned above has duplicated and fused ferredoxin-like domain (single polypeptide) and thus, the β6 of H. thermophilus (PDB identifier 4CZC) is equivalent to β2 of an individual ferredoxin-like domain of D. desulfuricans (PDB identifier 4UN1). We observe that in each of these proteins, both the ferredoxin-like domains of the barrel possess a histidine residue on the β2 strand. A superimposition of the siroheme decarboxylase structures from D. desulfuricans and H. thermophilus, reveals that the bound siroheme molecules are located at spatially distinct locations and conformation changes to a few side-chains of the siroheme moiety could allow the ferredoxin α + β barrel to accommodate two siroheme molecules simultaneously, without steric clashes.
We compared the various modes in which the ferredoxin-like domains may pack in the heme-binding ferredoxin α + β barrel families. We find that the ferredoxin-like domains may pack in two modes to form the barrel, which differ in the orientation of the constituent domains. Of the 18 families of ferredoxin α + β barrel superfamily (as classified by Pfam), Type-1 packing mode is seen in proteins belonging to 17 families of which proteins from the ABM, Cld, DyP and AsnC families are known bind heme and Type-2 is observed only in the heme-binding OxdA family proteins and the non-heme YqjZ-like proteins of the ABM family. Our analysis helps rationalize the underlying relationships between the different heme-binding sites and barrels of IsdG, OxdA and Cld/DyP/EfeB/HemQ proteins.
Dataset of ferredoxin α + β barrel superfamily proteins used in the present study
Representatives of the ferredoxin α + β barrel superfamily were selected from the SCOP and PDB databases after considering the following criteria. The presence of bound heme/heme-like ligand molecules to ferredoxin-like domain(s) was the primary criteria followed by a preference for structures without disordered regions and/or non-natural mutation(s) with maximum sequence length coverage. X-ray diffraction structures were preferred over NMR structures and the one with the highest resolution was selected. Representative structures that were selected included IsdG (PDB identifier 2ZDP_A), MhuD (3HX9_A), chlorite dismutase (PDB identifier 3NN1_A), DyP-type peroxidase (PDB identifier 3VXJ_A), EfeB (PDB identifier 3O72_A), HemQ (PDB identifier 1VDH_A) and aldoxime dehydratase (PDB identifier 3A16_A). Siroheme decarboxylase, which binds siroheme and whose structure was characterized recently, was also included in the representative dataset (PDB identifiers 4UN1_A, B, 4CZC_A) along with the representative of AsnC transcription regulator family (PDB identifier 2E7X_A). Other related proteins were obtained by sequence and structural similarity searches as outlined below (Additional file 2: Figure S2, Additional file 3).
The sequences of the selected representatives were used to initiate sequence similarity searches. In brief, iterative PSI-BLAST  (against UniProt database of 6 Apr, 2015, Number of letters: 172,526,934, Number of sequences: 461,263; E-value threshold of 1e-5), JackHMMER program from the HMMER3 package  (against: UniProtKB version 2014-06-17 and PDB version 2014-06-17; E-value threshold of 0.01), FFAS server  (against the regularly updated PDB, Pfam and SCOP databases) were used. MSAs of the various ferredoxin-like domains were generated using Profile Consistency Multiple Sequence Alignment (PCMA)  with default parameters.
As most families share a low sequence similarity, therefore, alignments generated by automated programs must be verified based on the actual structural data. Thus, a structure based manual correction of the MSAs was performed. This involved manual comparison of the automatically aligned regions and the actual structurally superimposing regions, verifying the accuracy of the MSA and manually correcting it if required. Particular care was taken to align the residues involved in forming conserved interactions including hydrogen bonding and interactions with heme moiety, and looking for subtle topological and structural features such as bulges, kinks, etc. that may help rationalize a distant evolutionary relationship .
Dali  and TopSearch  tools were used to evaluate the structural similarity of the complete barrels and the individual ferredoxin-like domains with other structures in the PDB. Dali evaluates protein structural similarity and provides a Z-score as a measure of statistical significance based on intermolecular distance matrices . TopSearch uses the TopMatch algorithm  to assess structural similarities among proteins while accounting for circular permutations and similarities in biological assemblies and asymmetric units. DaliLite program  was used for evaluating pairwise similarity among various structural domains. All protein structures were visualized and compared in the molecular visualization program PyMOL. Manual structural superimposition of structures was performed by defining the equivalent regions using the pair fitting command of PyMOL.
The topology diagrams of the ferredoxin α + β barrels for various protein families were sketched manually by referring to the three-dimensional structures.
Ethics approval and consent to participate
Consent for publication
Availability of data and material
All the structural data used for this study is freely available from the Protein Data Bank (http://www.rcsb.org/pdb/home/home.do) and the sequences from the UniProtKB resource (http://www.uniprot.org/).
GA is supported by a research fellowship from the CSIR, India. GK is supported by the Shyama Prasad Mukherjee Fellowship of the CSIR, India.
This work was supported by the XII five-year plan network project, Biodiscovery (BSC0120K) of the Council of Scientific and Industrial Research (CSIR) - Institute of Microbial Technology, Chandigarh, India. CSIR had no role in the design of the study and collection, analysis, and interpretation of data. CSIR did not contribute in writing the manuscript and the decision to submit the manuscript for publication.
- 8.Chauvaux S, Chevalier F, Le Dantec C, Fayolle F, Miras I, Kunst F, Beguin P. Cloning of a genetically unstable cytochrome P-450 gene cluster involved in degradation of the pollutant ethyl tert-butyl ether by Rhodococcus ruber. J Bacteriol. 2001;183(22):6551–7.CrossRefPubMedPubMedCentralGoogle Scholar
- 20.Kostan J, Sjoblom B, Maixner F, Mlynek G, Furtmuller PG, Obinger C, Wagner M, Daims H, Djinovic-Carugo K. Structural and functional characterisation of the chlorite dismutase from the nitrite-oxidizing bacterium “Candidatus Nitrospira defluvii”: identification of a catalytically important amino acid residue. J Struct Biol. 2010;172(3):331–42.CrossRefPubMedGoogle Scholar
- 24.Palmer DJ, Schroeder S, Lawrence AD, Deery E, Lobo SA, Saraiva LM, McLean KJ, Munro AW, Ferguson SJ, Pickersgill RW et al. The structure, function and properties of sirohaem decarboxylase--an enzyme with structural homology to a transcription factor family that is part of the alternative haem biosynthesis pathway. Mol Microbiol. 2014;93(2):247–61.CrossRefPubMedPubMedCentralGoogle Scholar
- 29.Hofbauer S, Hagmuller A, Schaffner I, Mlynek G, Krutzler M, Stadlmayr G, Pirker KF, Obinger C, Daims H, Djinovic-Carugo K et al. Structure and heme-binding properties of HemQ (chlorite dismutase-like protein) from Listeria monocytogenes. Arch Biochem Biophys. 2015;574:36–48.CrossRefPubMedPubMedCentralGoogle Scholar
- 36.Finn RD, Clements J, Eddy SR. HMMER web server: interactive sequence similarity searching. Nucleic Acids Res. 2011;39(Web Server issue):18.Google Scholar
- 38.Pearson WR. An Introduction to Sequence Similarity (“Homology”) Searching. Curr Protoc Bioinformatics/editoral board, Andreas D Baxevanis [et al.] 2013, 0 3: 10.1002/0471250953.bi0471250301s0471250942.
- 39.Sato T, Hara S, Matsui T, Sazaki G, Saijo S, Ganbe T, Tanaka N, Sugano Y, Shoda M. A unique dye-decolorizing peroxidase, DyP, from Thanatephorus cucumeris Dec 1: heterologous expression, crystallization and preliminary X-ray analysis. Acta Crystallogr Sect D: Biol Crystallogr. 2004;60(Pt 1):149–52.CrossRefGoogle Scholar
- 41.Zubieta C, Krishna SS, Kapoor M, Kozbial P, McMullan D, Axelrod HL, Miller MD, Abdubek P, Ambing E, Astakhova T, et al. Crystal structures of two novel dye-decolorizing peroxidases reveal a beta-barrel fold with a conserved heme-binding motif. Proteins. 2007;69(2):223–33.CrossRefPubMedGoogle Scholar
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