Crystallographic comparison of the estrogen and progesterone receptor’s ligand binding domains

The 2.8-Å crystal structure of the complex formed by estradiol and the human estrogen receptor-α ligand binding domain (hERαLBD) is described and compared with the recently reported structure of the progesterone complex of the human progesterone receptor ligand binding domain, as well as with similar structures of steroid/nuclear receptor LBDs solved elsewhere. The hormone-bound hERαLBD forms a distinctly different and probably more physiologically important dimer interface than its progesterone counterpart. A comparison of the specificity determinants of hormone binding reveals a common structural theme of mutually supported van der Waals and hydrogen-bonded interactions involving highly conserved residues. The previously suggested mechanism by which the estrogen receptor distinguishes estradiol’s unique 3-hydroxy group from the 3-keto function of most other steroids is now described in atomic detail. Mapping of mutagenesis results points to a coactivator-binding surface that includes the region around the “signature sequence” as well as helix 12, where the ligand-dependent conformation of the activation function 2 core is similar in all previously solved steroid/nuclear receptor LBDs. A peculiar crystal packing event displaces helix 12 in the hERαLBD reported here, suggesting a higher degree of dynamic variability than expected for this critical substructure.

Analysis and interpretation of cost data in randomised controlled trials: review of published studies

Objective To review critically the statistical methods used for health economic evaluations in randomised controlled trials where an estimate of cost is available for each patient in the study.

Intrinsic compressibility and volume compression in solvated proteins by molecular dynamics simulation at high pressure.

Constant pressure and temperature molecular dynamics techniques have been employed to investigate the changes in structure and volumes of two globular proteins, superoxide dismutase and lysozyme, under pressure. Compression (the relative changes in the proteins' volumes), computed with the Voronoi technique, is closely related with the so-called protein intrinsic compressibility, estimated by sound velocity measurements. In particular, compression computed with Voronoi volumes predicts, in agreement with experimental estimates, a negative bound water contribution to the apparent protein compression. While the use of van der Waals and molecular volumes underestimates the intrinsic compressibilities of proteins, Voronoi volumes produce results closer to experimental estimates. Remarkably, for two globular proteins of very different secondary structures, we compute identical (within statistical error) protein intrinsic compressions, as predicted by recent experimental studies. Changes in the protein interatomic distances under compression are also investigated. It is found that, on average, short distances compress less than longer ones. This nonuniform contraction underlines the peculiar nature of the structural changes due to pressure in contrast with temperature effects, which instead produce spatially uniform changes in proteins. The structural effects observed in the simulations at high pressure can explain protein compressibility measurements carried out by fluorimetric and hole burning techniques. Finally, the calculation of the proteins static structure factor shows significant shifts in the peaks at short wavenumber as pressure changes. These effects might provide an alternative way to obtain information concerning compressibilities of selected protein regions.

Significant discrepancies between van't Hoff and calorimetric enthalpies.

In this paper we show that the usual assumption in studies of the temperature variation of equilibrium constants for equilibria of the form A+B <-->AB that a plot of ln K vs. 1/T (K = equilibrium constant, T = temperature in degrees kelvin) is a straight line with slope equal to -delta HvH/R (delta HvH = van't Hoff or apparent enthalpy, R = gas constant) is not valid in many cases. In all the cases considered here, delta HvH is temperature dependent and is significantly different from the true or calorimetrically measured enthalpy, and the respective values for delta Cp are also significantly different.

Yersinia enterocolitica induces apoptosis in macrophages by a process requiring functional type III secretion and translocation mechanisms and involving YopP, presumably acting as an effector protein

Yersiniae, causative agents of plague and gastrointestinal diseases, secrete and translocate Yop effector proteins into the cytosol of macrophages, leading to disruption of host defense mechanisms. It is shown in this report that Yersinia enterocolitica induces apoptosis in macrophages and that this effect depends on YopP. Functional secretion and translocation mechanisms are required for YopP to act, strongly suggesting that this protein exerts its effect intracellularly, after translocation into the macrophages. YopP shows a high level of sequence similarity with AvrRxv, an avirulence protein from Xanthomonas campestris, a plant pathogen that induces programmed cell death in plant cells. This indicates possible similarities between the strategies used by pathogenic bacteria to elicit programmed cell death in both plant and animal hosts.