| 1. |
- Hallberg, B. M., et al.
(författare)
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A new scaffold for binding haem in the cytochrome domain of the extracellular flavocytochrome cellobiose dehydrogenase
- 2000
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Ingår i: Structure. - 0969-2126 .- 1878-4186. ; 8:1, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- Background: The fungal oxidoreductase cellobiose dehydrogenase (CDH) degrades both lignin and cellulose, and is the only known extracellular flavocytochrome. This haemoflavoenzyme has a multidomain organisation with a b-type cytochrome domain linked to a large flavodehydrogenase domain. The two domains can be separated proteolytically to yield a functional cytochrome and a flavodehydrogenase. Here, we report the crystal structure of the cytochrome domain of CDH. Results: The crystal structure of the b-type cytochrome domain of CDH from the wood-degrading fungus Phanerochaete chrysosporium has been determined at 1.9 Angstrom resolution using multiple isomorphous replacement ncluding anomalous scattering information. Three models of the cytochrome have been refined: the in vitro prepared cytochrome in its redox-inactive state (pH 7.5) and redox-active state (pH 4.6), as well as the naturally occurring cytochrome fragment. Conclusions: The 190-residue long cytochrome domain of CDH folds as a beta sandwich with the topology of the antibody Fab V-H domain. The haem iron is ligated by Met65 and His 163, which confirms previous results from spectroscopic studies. This is only the second example of a b-type cytochrome with this ligation, the first being cytochrome b(562). The haem-propionate groups are surface exposed and, therefore, might play a role in the association between the cytochrome and flavoprotein domain, and in interdomain electron transfer. There are no large differences in overall structure of the cytochrome at redoxactive pH as compared with the inactive form, which excludes the possibility that pH-dependent redox inactivation results from partial denaturation. From the electron-density map of the naturally occurring cytochrome, we conclude that it corresponds to the proteolytically prepared cytochrome domain.
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| 2. |
- Zhang, Rong guang, et al.
(författare)
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Structure of Escherichia coli ribose-5-phosphate isomerase : a ubiquitous enzyme of the pentose phosphate pathway and the Calvin cycle
- 2003
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Ingår i: Structure. - 0969-2126 .- 1878-4186. ; 11:1, s. 31-42
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Tidskriftsartikel (refereegranskat)abstract
- Ribose-5-phosphate isomerase A (RpiA; EC 5.3.1.6) interconverts ribose-5-phosphate and ribulose-5-phosphate. This enzyme plays essential roles in carbohydrate anabolism and catabolism; it is ubiquitous and highly conserved. The structure of RpiA from Escherichia coli was solved by multiwavelength anomalous diffraction (MAD) phasing, and refined to 1.5 A resolution (R factor 22.4%, R(free) 23.7%). RpiA exhibits an alpha/beta/(alpha/beta)/beta/alpha fold, some portions of which are similar to proteins of the alcohol dehydrogenase family. The two subunits of the dimer in the asymmetric unit have different conformations, representing the opening/closing of a cleft. Active site residues were identified in the cleft using sequence conservation, as well as the structure of a complex with the inhibitor arabinose-5-phosphate at 1.25 A resolution. A mechanism for acid-base catalysis is proposed.
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| 3. |
- Holmner, Åsa, et al.
(författare)
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Novel binding site identified in a hybrid between cholera toxin and heat-labile enterotoxin: 1.9 A crystal structure reveals the details.
- 2004
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Ingår i: Structure (London, England : 1993). - : Elsevier BV. - 0969-2126 .- 1878-4186. ; 12:9, s. 1655-67
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid between the B subunits of cholera toxin and Escherichia coli heat-labile enterotoxin has been described, which exhibits a novel binding specificity to blood group A and B type 2 determinants. In the present investigation, we have determined the crystal structure of this protein hybrid, termed LCTBK, in complex with the blood group A pentasaccharide GalNAcalpha3(Fucalpha2)Galbeta4(Fucalpha3)GlcNAcbeta, confirming not only the novel binding specificity but also a distinct new oligosaccharide binding site. Binding studies revealed that the new specificity can be ascribed to a single mutation (S4N) introduced into the sequence of Escherichia coli heat-labile enterotoxin. At a resolution of 1.9 A, the new binding site is resolved in excellent detail. Main features include a complex network of water molecules, which is well preserved by the parent toxins, and an unexpectedly modest contribution to binding by the critical residue Asn4, which interacts with the ligand only via a single water molecule.
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| 4. |
- Lindkvist, Karin, et al.
(författare)
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Crystal structure of a SEA variant in complex with MHC class II reveals the ability of SEA to crosslink MHC molecules
- 2002
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Ingår i: Structure. - 0969-2126. ; 10:12, s. 1619-1626
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Tidskriftsartikel (refereegranskat)abstract
- Although the biological properties of staphylococcal enterotoxin A (SEA) have been well characterized, structural insights into the interaction between SEA and major histocompatibilty complex (MHC) class II have only been obtained by modeling. Here, the crystal structure of the D227A variant of SEA in complex with human MHC class II has been determined by X-ray crystallography. SEA(D227A) exclusively binds with its N-terminal domain to the alpha chain of HLA-DR1. The ability of one SEA molecule to crosslink two MHC molecules was modeled. It shows that this SEA molecule cannot interact with the T cell receptor (TCR) while a second SEA molecule interacts with MHC. Because of its relatively low toxicity, the D227A variant of SEA is used in tumor therapy.
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| 5. |
- Nevskaya, Natasha, et al.
(författare)
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Archaeal ribosomal protein L1: the structure provides new insights into RNA binding of the L1 protein family
- 2000
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Ingår i: Structure. - 0969-2126. ; 8:4, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Background: L1 is an important primary rRNA-binding protein, as well as a translational repressor that binds mRNA. It was shown that L1 proteins from some bacteria and archaea are functionally interchangeable within the ribosome and in the repression of translation. The crystal structure of bacterial L1 from Thermus thermophilus (TthL1) has previously been determined. Results: We report here the first structure of a ribosomal protein from archaea, L1 from Methanococcus jannaschii (MjaL1). The overall shape of the two-domain molecule differs dramatically from that of its bacterial counterpart (TthL1) because of the different relative orientations of the domains. Two strictly conserved regions of the amino acid sequence, each belonging to one of the domains and positioned close to each other in the interdomain cavity of TthL1, are separated by about 25 Å in MjaL1 owing to a significant opening of the structure. These regions are structurally highly conserved and are proposed to be the specific RNA-binding sites. Conclusions: The unusually high RNA-binding affinity of MjaL1 might be explained by the exposure of its highly conserved regions. The open conformation of MjaL1 is strongly stabilized by nonconserved interdomain interactions and suggests that the closed conformations of L1 (as in TthL1) open upon RNA binding. Comparison of the two L1 protein structures reveals a high conformational variability of this ribosomal protein. Determination of the MjaL1 structure offers an additional variant for fitting the L1 protein into electron-density maps of the 50S ribosomal subunit.
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| 6. |
- Hendrickson, WA, et al.
(författare)
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New look and new outlook
- 2002
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Ingår i: STRUCTURE. - 0969-2126. ; 10:1, s. 1-1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Lindqvist, Y
(författare)
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A new kinase fold
- 2003
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Ingår i: Structure (London, England : 1993). - : Elsevier BV. - 0969-2126. ; 11:3, s. 241-242
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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