Structural basis for the nuclease activity of a bacteriophage large terminase

The DNA-packaging motor in tailed bacteriophages requires nuclease activity to ensure that the genome is packaged correctly. This nuclease activity is tightly regulated as the enzyme is inactive for the duration of DNA translocation. Here, we report the X-ray structure of the large terminase nuclease domain from bacteriophage SPP1. Similarity with the RNase H family endonucleases allowed interactions with the DNA to be predicted. A structure-based alignment with the distantly related T4 gp17 terminase shows the conservation of an extended β-sheet and an auxiliary β-hairpin that are not found in other RNase H family proteins. The model with DNA suggests that the β-hairpin partly blocks the active site, and in vivo activity assays show that the nuclease domain is not functional in the absence of the ATPase domain. Here, we propose that the nuclease activity is regulated by movement of the β-hairpin, altering active site access and the orientation of catalytically essential residues

Recent updates on the Maser Monitoring Organisation

The Maser Monitoring Organisation (M2O) is a research community of telescope operators, astronomy researchers and maser theoreticians pursuing a joint goal of reaching a deeper understanding of maser emission and exploring its variety of uses as tracers of astrophysical events. These proceedings detail the origin, motivations and current status of the M2O, as was introduced at the 2021 EVN symposium

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Cryo-EM structures of the autoinhibited E. coli ATP synthase in three rotational states

A molecular model that provides a framework for interpreting the wealth of functional information obtained on the E. coli F-ATP synthase has been generated using cryo-electron microscopy. Three different states that relate to rotation of the enzyme were observed, with the central stalk’s ε subunit in an extended autoinhibitory conformation in all three states. The Fo motor comprises of seven transmembrane helices and a decameric c-ring and invaginations on either side of the membrane indicate the entry and exit channels for protons. The proton translocating subunit contains near parallel helices inclined by ~30° to the membrane, a feature now synonymous with rotary ATPases. For the first time in this rotary ATPase subtype, the peripheral stalk is resolved over its entire length of the complex, revealing the F1 attachment points and a coiled-coil that bifurcates toward the membrane with its helices separating to embrace subunit a from two sides.MOE (Min. of Education, S’pore)Published versio

L-tryptophan binding constants (K_d) of three wild type and three mutant TRAP.

<p>L-tryptophan binding constants (K_d) of three wild type and three mutant TRAP.</p

Data collection and refinement statistics for <i>B. subtilis</i> S72N TRAP.

<p>Values in parentheses are for the highest resolution shell.</p>a<p><i>R_merge</i>  =  ∑<i>_hkl</i>∑_i|<i>I_i(h)</i> - <<i>I(h)></i>|/∑<i>_hkl</i>∑_i<i>I_i(h)</i>, where <i>I(h)</i> is intensity of reflection <i>h</i>, <<i>I(h)></i> is average value of intensity, the sum ∑<i>_hkl</i> is over all measured reflections and the sum ∑_i is over <i>i</i> measurements of a reflection.</p>b<p>Crystallographic <i>R  = </i> ∑<i>_hkl</i>||<i>F_obs</i> - <i>F_calc</i>||/∑<i>_hkl</i>|<i>F_obs|</i>, <i>R_free</i> was calculated using a randomly chosen set of reflections that were excluded from the refinement.</p

Structural differences between 11-subunit and 12-subunit TRAP.

<p>(<b>A</b>) Comparison of the <i>B. subtilis</i> wild type (red) and S72N mutant TRAP (blue). Two neighboring subunits were least-square fitted using main chain atoms of the subunit on the left. The C-terminal residues that are pivoted out of the subunit interface in S72N TRAP are highlighted in white on the wild type TRAP, starting from residue 69. (<b>B</b>) C-terminal residues E69 and M70 are shown in sticks with main chain in yellow and side chains in turquoise, the rest of each subunit is shown in ribbons. The weighted <i>F</i>_o – <i>F</i>_c omit maps, contoured at 2σ, were calculated after omitting residues 69 and 70 from the final model and 10 cycles of refinement.</p