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  • 1. Fedulova, Natalia
    et al.
    Raffalli-Mathieu, Françoise
    Mannervik, Bengt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.
    Characterization of porcine Alpha-class glutathione transferase A1-12011Inngår i: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 507, nr 2, s. 205-211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An Alpha-class glutathione transferase (GST) has been cloned from pig gonads. In addition to two conservative point mutations our nucleotide sequence presents a frame shift resulting from a missing A as compared to a previously published porcine GST A1-1 sequence. The deduced C-terminal amino-acid segment of the protein differs between the two variants. Repeated sequencing of cDNA isolated from different tissues and animals ruled out the possibility of a cloning artifact, and the deduced amino acid sequence of our clone showed higher similarity to related mammalian GST sequences. Hereafter, we refer to our cloned enzyme as GST A1-1 and to the previously published enzyme as GST A1-1(∗). The study of the tissue distribution of the GSTA1 mRNA revealed high expression levels in many organs, in particular adipose tissue, liver, and pituitary gland. Porcine GST A1-1 was expressed in Escherichia coli and its kinetic properties were determined using alternative substrates. The catalytic activity in steroid isomerization reactions was at least 10-fold lower than the corresponding values for porcine GST A2-2, whereas the activity with 1-chloro-2,4-dinitrobenzene was approximately 8-fold higher. Differences in the H-site residues of mammalian Alpha-class GSTs may explain the catalytic divergence.

  • 2. Josephy, P. David
    et al.
    Pan, Dan
    Ianni, Michael D.
    Mannervik, Bengt
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.
    Functional studies of single-nucleotide polymorphic variants of human glutathione transferase T1-1 involving residues in the dimer interface2011Inngår i: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 513, nr 2, s. 87-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glutathione transferase T1-1 catalyses detoxication and bioactivation processes in which glutathione conjugates are formed from endogenous and xenobiotic substrates, including alkylating agents and halogenated alkanes. Although the common null polymorphism of the human GSTT1 gene has been studied extensively, little is known about the consequences of GSTT1 single-nucleotide polymorphisms (SNPs). Here, we have examined the effects of two SNPs that alter amino acid residues in the dimer interface of the GST T1-1 protein and one that causes a conservative substitution in the core of the subunit. Variant proteins were expressed in an Escherichia coli strain in which the metabolism of ethylene dibromide to a glutathione conjugate leads to lacZ reversion mutations. We measured the kinetic properties of the enzymes with the characteristic substrate 1,2-epoxy-3-(p-nitrophenoxy)propane (EPNP) and determined the specific activities with several other substrates. Circular dichroism spectroscopy was used to measure protein thermal denaturation profiles. Variant T104P, which has been reported as inactive, showed weak but detectable activity with each substrate. Variant R76S was expressed at lower levels and showed much-reduced thermal stability. The results are interpreted in the context of the three-dimensional structure of human GST T1-1.

  • 3.
    Luo, Jinghui
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Gräslund, Astrid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Ribonucleotide reductase inhibition by p-alkoxyphenols studied by molecular docking and molecular dynamics simulations.2011Inngår i: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 516, nr 1, s. 29-34Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ribonucleotide reductase (RNR) is necessary for production of the precursor deoxyribonucleotides for DNA synthesis. Class Ia RNR functions via a stable free radical in one of the two components protein R2. The enzyme mechanism involves long range (proton coupled) electron transfer between protein R1 and the tyrosyl radical in protein R2. Earlier experimental studies showed that p-alkoxyphenols inhibit RNR. Here, molecular docking and molecular dynamics simulations involving protein R2 suggest an inhibition mechanism for p-alkoxyphenols . A low energy binding pocket is identified in protein R2. The preferred configuration provides a structural basis explaining their specific binding to the Escherichia coli and mouse R2 proteins. Trp48 (E. coli numbering), on the electron transfer pathway, is involved in the interactions with the inhibitors. The relative order of the binding energies calculated for the phenol derivatives to protein R2 is correlated with earlier experimental data on inhibition efficiency, in turn related to increasing size of the hydrophobic alkyl substituents. Using the configuration identified by molecular docking as a starting point for molecular dynamics simulations, we find that the p-allyloxyphenol interrupts the catalytic electron transfer pathway of the R2 protein by forming hydrogen bonds with Trp48 and Asp237, thus explaining the inhibitory activity of p-alkoxyphenols.

  • 4.
    Löfgren Söderberg, Kajsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Guterstam, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.
    Langel, Ülo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för neurokemi.
    Gräslund, Astrid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Targeting prion propagation using peptide constructs with signal sequence motifs2014Inngår i: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 564, s. 254-261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Synthetic peptides with sequences derived from the cellular prion protein (PrPc) unprocessed N-terminus are able to counteract the propagation of proteinase K resistant prions (PrPRes, indicating the presence of the prion isoform of the prion protein) in cell cultures (Lofgren et al., 2008). The anti-prion peptides have characteristics like cell penetrating peptides (CPPs) and consist of the prion protein hydrophobic signal sequence followed by a polycationic motif (residues KKRPKP), in mouse PrPc corresponding to residues 1-28. Here we analyze the sequence elements required for the anti-prion effect of KKRPKP-conjugates. Neuronal GT1-1 cells were infected with either prion strain RML or 22L Variable peptide constructs originating from the mPrP(1-28) sequence were analyzed for anti-prion effects, measured as disappearance of proteinase K resistant prions (PrPRes) in the infected cell cultures. We find that even a 5 amino acid N-terminal shortening of the signal peptide abolishes the anti-prion effect. We show that the signal peptide from PrPc can be replaced with the signal peptide from the Neural cell adhesion molecule-1; NCAMl(1-19), with a retained capacity to reduce PrPRes levels. The anti-prion effect is lost if the polycationic N-terminal PrPc-motif is conjugated to any conventional CPP, such as TAT(48-60), transportan-10 or penetratin. We propose a mechanism by which a signal peptide from a secretory or cell surface protein acts to promote the transport of a prion-binding polycationic PrPc-motif to a subcellular location where prion conversion occurs (most likely the Endosome Recycling Compartment), thereby targeting prion propagation.

  • 5. Santacruz-Perez, Carolina
    et al.
    Pegos, Vanessa Rodrigues
    Honorato, Rodrigo V.
    Verli, Hugo
    Lindahl, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Ribeiro Goncalves Barbosa, Joao Alexandre
    Balan, Andrea
    A specific interdomain interaction preserves the structural and binding properties of the ModA protein from the phytopathogen Xanthomonas citri domain interaction and transport in ModA2013Inngår i: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 539, nr 1, s. 20-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The periplasmic-binding proteins in ATP-binding cassette systems (ABC Transporters) are responsible for the capture and delivery of ligands to their specific transporters, triggering a series of ATP-driven conformational changes that leads to the transport of the ligand. Structurally consisting of two lobes, the proteins change conformation after interaction with the ligand. The structure of the molybdate-binding protein (ModA) from Xanthomonas citri, bound to molybdate, was previously solved by our group and an interdomain interaction, mediated by a salt bridge between K127 and D59, apparently supports the binding properties and keeps the domains closed. To determinate the importance of this interaction, we built two ModA mutants, K127S and D59A, and analysed their functional and structural properties. Based on a set of spectroscopic experiments, crystallisation trials, structure determination and molecular dynamics (MD) simulations, we showed that the salt bridge is essential to maintain the structure and binding properties. Additionally, the MD simulations revealed that this mutant adopted a more compact structure that packed down the ligand-binding pocket. From the closed bound to open structure, the positioning of the helices forming the dipole and the salt bridge are essential to induce an intermediate state.

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