2506186
Model-independent determination of the top Yukawa coupling from LHC and ILC
We show how a measurement of the process pp→tt̄H0+X at the Large Hadron Collider (LHC) and a measurement of the Higgs boson branching ratios BR(H0→bb̄) and BR(H0→W+W-) at a future linear electron positron collider (ILC) can be combined to extract a value of the top quark Yukawa coupling in a model-independent way. We find that for masses with 120 GeV/c2<mH<200 GeV/c2 a measurement precision of 15% including systematic uncertainties can be achieved for integrated luminosities of 300 fb-1 at the LHC and 500 fb-1 at the ILC at a centre-of-mass energy of 350 GeV. 
8372632
Investigation of the Discovery Potential for Higgs Bosons of the Minimal Supersymmetric Extension of the Standard Model (MSSM) with ATLAS
The discovery potential of the ATLAS experiment at the LHC for Higgs bosons of the MSSM is discussed. Several CP conserving and one CP violating benchmark scenario are investigated.
117172015
The Higgs Boson: Still Elusive After 40 Years
117936692
TPC with GEM readout for TESLA
A Time Projection Chamber (TPC) is proposed as the main tracking device for the detector at the future e+e− linear accelerator now studied in Europe. The performance requirements and the basic design using a Gas Electron Multiplier (GEM) as the readout device are described. Some preliminary R&D results are discussed.
118275903
CP Tests and the Weak Dipole Moment in τ-Pair Production at LEP
Tests of CP in variance in the reaction e +e− →τ+τ− on the Z 0 peak are reviewed. Averaging the present LEP measurements, upper limits on the real and imaginary parts of the weak dipole moment of the τ lepton of ∣Re(d τ w (M Z 2 ))∣ < 3.3 • 10−18 ecm and ∣Im(d τ w (M Z 2 ))∣ < 9.8 • 10−18 ecm with 95% c.l. are obtained.
122077797
SEARCHES FOR NEW PHYSICS AT LEP
5803090
Structural basis for cooperative DNA binding by two dimers of the multidrug-binding protein QacR.
The Staphylococcus aureus multidrug-binding protein QacR represses transcription of the qacA multidrug transporter gene and is induced by multiple structurally dissimilar drugs. QacR is a member of the TetR/CamR family of transcriptional regulators, which share highly homologous N-terminal DNA-binding domains connected to seemingly non-homologous ligand-binding domains. Unlike other TetR members, which bind approximately 15 bp operators, QacR recognizes an unusually long 28 bp operator, IR1, which it appears to bind cooperatively. To elucidate the DNA-binding mechanism of QacR, we determined the 2.90 A resolution crystal structure of a QacR-IR1 complex. Strikingly, our data reveal that the DNA recognition mode of QacR is distinct from TetR and involves the binding of a pair of QacR dimers. In this unique binding mode, recognition at each IR1 half-site is mediated by a complement of DNA contacts made by two helix-turn-helix motifs. The inferred cooperativity does not arise from cross-dimer protein-protein contacts, but from the global undertwisting and major groove widening elicited by the binding of two QacR dimers.
38152937
Structural Mechanisms of QacR Induction and Multidrug Recognition
The Staphylococcus aureus multidrug binding protein QacR represses transcription of the qacA multidrug transporter gene and is induced by structurally diverse cationic lipophilic drugs. Here, we report the crystal structures of six QacR-drug complexes. Compared to the DNA bound structure, drug binding elicits a coil-to-helix transition that causes induction and creates an expansive multidrug-binding pocket, containing four glutamates and multiple aromatic and polar residues. These structures indicate the presence of separate but linked drug-binding sites within a single protein. This multisite drug-binding mechanism is consonant with studies on multidrug resistance transporters.
19913942
Crystal Structures of QacR-Diamidine Complexes Reveal Additional Multidrug-binding Modes and a Novel Mechanism of Drug Charge Neutralization*
The Staphylococcus aureus multidrug-binding protein QacR represses transcription of the plasmid-encoded membrane protein QacA, a multidrug efflux transporter. QacR is induced by multiple structurally dissimilar monovalent and bivalent cationic lipophilic compounds, many of which are effluxed from the cell by QacA via the proton motive force. The multidrug-binding pocket of QacR has been shown to be quite extensive and features several glutamates and multiple aromatic residues. To date, the structure of only one QacR-bivalent cationic drug complex (that of QacR bound to dequalinium) has been determined, and how other longer or shorter bivalent cationic compounds bind is unknown. Here we report the crystal structures of QacR bound to two cytotoxic bivalent diamidines, pentamidine and hexamidine. These compounds are structurally similar, differing by only one methylene carbon in the alkyl chain linker. However, this small difference results in very dissimilar binding modes. Similar to dequalinium, hexamidine spans the multidrug-binding pocket, and its positively charged benzamidine groups are neutralized by residues Glu-57 and Glu-120. Pentamidine binds QacR in a novel fashion whereby one of its benzamidine groups interacts with residue Glu-63, and the other is neutralized by carbonyl and side chain oxygen atoms. Thus, these structures demonstrate that a formal negative charge is not a prerequisite for binding positively charged drugs and underscore the versatility of the QacR and, likely, all multidrug-binding pockets.
22785877
Structures of the pleiotropic translational regulator Hfq and an Hfq-RNA complex: a bacterial Sm-like protein.
In prokaryotes, Hfq regulates translation by modulating the structure of numerous RNA molecules by binding preferentially to A/U-rich sequences. To elucidate the mechanisms of target recognition and translation regulation by Hfq, we determined the crystal structures of the Staphylococcus aureus Hfq and an Hfq-RNA complex to 1.55 and 2.71 A resolution, respectively. The structures reveal that Hfq possesses the Sm-fold previously observed only in eukaryotes and archaea. However, unlike these heptameric Sm proteins, Hfq forms a homo-hexameric ring. The Hfq-RNA structure reveals that the single-stranded hepta-oligoribonucleotide binds in a circular conformation around a central basic cleft, whereby Tyr42 residues from adjacent subunits stack with six of the bases, and Gln8, outside the Sm motif, provides key protein-base contacts. Such binding suggests a mechanism for Hfq function.
17287147
Structural Basis of Core Promoter Recognition in a Primitive Eukaryote
Transcription start site selection in eukaryotes is mediated through combinations of the TATA, initiator (Inr), and downstream promoter elements (DPE). In Trichomonas vaginalis, a parabasalian flagellate thought to represent an ancient eukaryote lineage, the Inr appears to be solely responsible for start site selection and is recognized by the initiator binding protein 39 kDa (IBP39). IBP39 contains an N-terminal Inr binding domain (IBD) connected via a flexible linker to a C-terminal domain (C domain). Here we present crystal structures of the apoIBD and IBD-Inr complexes and the C domain. The IBD structures reveal a winged-helix motif with prokaryotic and eukaryotic features and a scaffold similar to that of ETS-family proteins. The C domain structure and biochemical studies indicate that it interacts with the T. vaginalis RNAP II large subunit C-terminal domain. These data suggest that binding of IBP39 to the Inr directly recruits RNAP II and in this way initiates transcription.