| 1. |
- Frauenfeld, Jens, et al.
(author)
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A saposin-lipoprotein nanoparticle system for membrane proteins
- 2016
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In: Nature Methods. - : Nature Publishing Group. - 1548-7091 .- 1548-7105. ; 13:4, s. 345-351
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Journal article (peer-reviewed)abstract
- A limiting factor in membrane protein research is the ability to solubilize and stabilize such proteins. Detergents are used most often for solubilizing membrane proteins, but they are associated with protein instability and poor compatibility with structural and biophysical studies. Here we present a saposin-lipoprotein nanoparticle system, Salipro, which allows for the reconstitution of membrane proteins in a lipid environment that is stabilized by a scaffold of saposin proteins. We demonstrate the applicability of the method on two purified membrane protein complexes as well as by the direct solubilization and nanoparticle incorporation of a viral membrane protein complex from the virus membrane. Our approach facilitated high-resolution structural studies of the bacterial peptide transporter PeptT(S02) by single-particle cryo-electron microscopy (cryo-EM) and allowed us to stabilize the HIV envelope glycoprotein in a functional state.
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| 2. |
- Gurmu, Daniel, et al.
(author)
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Expression, purification, crystallization and preliminary X-ray analysis of ORF60, the small subunit (R2) of ribonucleotide reductase from Kaposi's sarcoma-associated herpesvirus (KSHV)
- 2010
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In: Acta Crystallographica. Section F. - 1744-3091 .- 1744-3091. ; 66, s. 734-737
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Journal article (peer-reviewed)abstract
- Ribonucleotide reductase (RNR) is responsible for converting ribonucleotides to deoxyribonucleotides, which are the building blocks of DNA. The enzyme is present in all life forms as well as in some large DNA viruses such as herpesviruses. The alpha-herpesviruses and gamma-herpesviruses encode two class Ia RNR subunits, R1 and R2, while the beta-herpesvirus subfamily only encode an inactive R1 subunit. Here, the crystallization of the R2 subunit of RNR encoded by the ORF60 gene from the oncovirus Kaposi's sarcoma-associated gamma-herpesvirus (KSHV) is reported. These are the first crystals of a viral R2 subunit; the use of in situ proteolysis with chymotrypsin and the addition of hexamine cobalt(III) chloride that were necessary to obtain crystals are described. Optimization of the crystallization conditions yielded crystals that diffracted to 2.0 angstrom resolution. The crystals belonged to space group P2(1), with unit-cell parameters a = 63.9, b = 71.2, c = 71.8 angstrom, alpha = 90, beta = 106.7, gamma = 90 degrees. The data set collected was 95.3% complete, with an R-merge of 9.6%. There are two molecules in the asymmetric unit, corresponding to a solvent content of 43.4%.
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| 3. |
- Herman, Maria Dolores, et al.
(author)
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Structures of BIR domains from human NAIP and cIAP2
- 2009
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In: Acta Crystallographica. Section F. - 1744-3091 .- 1744-3091. ; 65, s. 1091-1096
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Journal article (peer-reviewed)abstract
- The inhibitor of apoptosis (IAP) family of proteins contains key modulators of apoptosis and inflammation that interact with caspases through baculovirus IAP-repeat (BIR) domains. Overexpression of IAP proteins frequently occurs in cancer cells, thus counteracting the activated apoptotic program. The IAP proteins have therefore emerged as promising targets for cancer therapy. In this work, X-ray crystallography was used to determine the first structures of BIR domains from human NAIP and cIAP2. Both structures harbour an N-terminal tetrapeptide in the conserved peptide-binding groove. The structures reveal that these two proteins bind the tetrapeptides in a similar mode as do other BIR domains. Detailed interactions are described for the P1'-P4' side chains of the peptide, providing a structural basis for peptide-specific recognition. An arginine side chain in the P3' position reveals favourable interactions with its hydrophobic moiety in the binding pocket, while hydrophobic residues in the P2' and P4' pockets make similar interactions to those seen in other BIR domain-peptide complexes. The structures also reveal how a serine in the P1' position is accommodated in the binding pockets of NAIP and cIAP2. In addition to shedding light on the specificity determinants of these two proteins, the structures should now also provide a framework for future structure-based work targeting these proteins.
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| 4. |
- Martinez Molina, Daniel, et al.
(author)
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Monitoring Drug Target Engagement in Cells and Tissues Using the Cellular Thermal Shift Assay
- 2013
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In: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 341:6141, s. 84-87
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Journal article (peer-reviewed)abstract
- The efficacy of therapeutics is dependent on a drug binding to its cognate target. Optimization of target engagement by drugs in cells is often challenging, because drug binding cannot be monitored inside cells. We have developed a method for evaluating drug binding to target proteins in cells and tissue samples. This cellular thermal shift assay (CETSA) is based on the biophysical principle of ligand-induced thermal stabilization of target proteins. Using this assay, we validated drug binding for a set of important clinical targets and monitored processes of drug transport and activation, off-target effects and drug resistance in cancer cell lines, as well as drug distribution in tissues. CETSA is likely to become a valuable tool for the validation and optimization of drug target engagement.
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| 5. |
- Patton, Gregory C., et al.
(author)
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Cofactor mobility determines reaction outcome in the IMPDH and GMPR (beta-alpha)(8) barrel enzymes
- 2011
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In: Nature Chemical Biology. - 1552-4450 .- 1552-4469. ; 7, s. 950-958
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Journal article (peer-reviewed)abstract
- Inosine monophosphate dehydrogenase (IMPDH) and guanosine monophosphate reductase (GMPR) belong to the same structural family, share a common set of catalytic residues and bind the same ligands. The structural and mechanistic features that determine reaction outcome in the IMPDH and GMPR family have not been identified. Here we show that the GMPR reaction uses the same intermediate E-XMP(star) as IMPDH, but in this reaction the intermediate reacts with ammonia instead of water. A single crystal structure of human GMPR type 2 with IMP and NADPH fortuitously captures three different states, each of which mimics a distinct step in the catalytic cycle of GMPR. The cofactor is found in two conformations: an 'in' conformation poised for hydride transfer and an 'out' conformation in which the cofactor is 6 angstrom from IMP. Mutagenesis along with substrate and cofactor analog experiments demonstrate that the out conformation is required for the deamination of GMP. Remarkably, the cofactor is part of the catalytic machinery that activates ammonia.
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