Crystallization and preliminary X-ray analysis of the Tet-repressor/operator complex.
Three crystal forms of the repressor protein TetR class D in complex with the palindromic 17 bp operator sequence containing T overhangs on both sides were obtained by hanging-drop vapor-diffusion methods using PEG 4000 and PEG monomethylether 5000 as precipitants. Although the crystallization conditions were very similar, up to three different crystal forms were observed in the same drop. The space groups are monoclinic C2, P21 and hexagonal P6122. The asymmetric units of the latter two crystal forms contain one repressor-operator complex. The crystal structures of these forms were solved by molecular replacement using the Tet-repressor molecule of the complex with tetracycline as a search model.
Background ::: A major complication associated with cardiac surgery is excessive and prolonged bleeding in the perioperative period. Improving coagulation by inhibiting fibrinolysis, primarily through inhibition of plasmin activity (PLact) with antifibrinolytics such as tranexamic acid (TXA) has been a pharmacological mainstay in cardiac surgical patients. Despite its almost ubiquitous use, the temporal and regional modulation of PLact profiles by TXA remain unexplored. Accordingly, the present study developed a fluorogenic-microdialysis system to measure in-vivo dynamic changes in PLact following TXA administration in a large animal model.