Crystal structure of the ferritin from the hyperthermophilic archaeal anaerobe Pyrococcus furiosus

The crystal structure of the ferritin from the archaeon, hyperthermophile and anaerobe Pyrococcus furiosus (PfFtn) is presented. While many ferritin structures from bacteria to mammals have been reported, until now only one was available from archaea, the ferritin from Archaeoglobus fulgidus (AfFtn). The PfFtn 24-mer exhibits the 432 point-group symmetry that is characteristic of most ferritins, which suggests that the 23 symmetry found in the previously reported AfFtn is not a common feature of archaeal ferritins. Consequently, the four large pores that were found in AfFtn are not present in PfFtn. The structure has been solved by molecular replacement and refined at 2.75-Å resolution to R = 0.195 and Rfree = 0.247. The ferroxidase center of the aerobically crystallized ferritin contains one iron at site A and shows sites B and C only upon iron or zinc soaking. Electron paramagnetic resonance studies suggest this iron depletion of the native ferroxidase center to be a result of a complexation of iron by the crystallization salt. The extreme thermostability of PfFtn is compared with that of eight structurally similar ferritins and is proposed to originate mostly from the observed high number of intrasubunit hydrogen bonds. A preservation of the monomer fold, rather than the 24-mer assembly, appears to be the most important factor that protects the ferritin from inactivation by heat

Measuring the burden of arboviral diseases: the spectrum of morbidity and mortality from four prevalent infections

<p>Abstract</p> <p>Background</p> <p>Globally, arthropod-borne virus infections are increasingly common causes of severe febrile disease that can progress to long-term physical or cognitive impairment or result in early death. Because of the large populations at risk, it has been suggested that these outcomes represent a substantial health deficit not captured by current global disease burden assessments.</p> <p>Methods</p> <p>We reviewed newly available data on disease incidence and outcomes to critically evaluate the disease burden (as measured by disability-adjusted life years, or DALYs) caused by yellow fever virus (YFV), Japanese encephalitis virus (JEV), chikungunya virus (CHIKV), and Rift Valley fever virus (RVFV). We searched available literature and official reports on these viruses combined with the terms "outbreak(s)," "complication(s)," "disability," "quality of life," "DALY," and "QALY," focusing on reports since 2000. We screened 210 published studies, with 38 selected for inclusion. Data on average incidence, duration, age at onset, mortality, and severity of acute and chronic outcomes were used to create DALY estimates for 2005, using the approach of the current Global Burden of Disease framework.</p> <p>Results</p> <p>Given the limitations of available data, nondiscounted, unweighted DALYs attributable to YFV, JEV, CHIKV, and RVFV were estimated to fall between 300,000 and 5,000,000 for 2005. YFV was the most prevalent infection of the four viruses evaluated, although a higher proportion of the world's population lives in countries at risk for CHIKV and JEV. Early mortality and long-term, related chronic conditions provided the largest DALY components for each disease. The better known, short-term viral febrile syndromes caused by these viruses contributed relatively lower proportions of the overall DALY scores.</p> <p>Conclusions</p> <p>Limitations in health systems in endemic areas undoubtedly lead to underestimation of arbovirus incidence and related complications. However, improving diagnostics and better understanding of the late secondary results of infection now give a first approximation of the current disease burden from these widespread serious infections. Arbovirus control and prevention remains a high priority, both because of the current disease burden and the significant threat of the re-emergence of these viruses among much larger groups of susceptible populations.</p

Variation of molecular alignment as a means of resolving orientational ambiguities in protein structures from dipolar couplings

Residual dipolar couplings for pairs of proximate magnetic nuclei in macromolecules can easily be measured using highresolution NMR methods when the molecules are dissolved in dilute liquid crystalline media. The resulting couplings can in principle be used to constrain the relative orientation of molecular fragments in macromolecular systems to build a complete structure. However, determination of relative fragment orientations based on a single set of residual dipolar couplings is inherently hindered by the multi-valued nature of the angular dependence of the dipolar interaction. Even with unlimited dipolar data, this gives rise to a fourfold degeneracy in fragment orientations. In this Communication, we demonstrate a procedure based on an order tensor analysis that completely removes this degeneracy by combining residual dipolar coupling measurements from two alignment media. Application is demonstrated on 15 N – 1 H residual dipolar coupling data acquired on the protein zinc rubredoxin from Clostridium pasteurianum dissolved in two different bicell

Structural basis for thermostability in aporubredoxins from Pyrococcus furiosus and Clostridium pasteurianum

The structures of apo- and holorubredoxins from Pyrococcus furiosus (PfRd) and Clostridium pasteurianum (CpRd) have been investigated and compared using residual dipolar couplings to probe the origin of thermostability. In the native, metal (Fe or Zn) containing form, both proteins can maintain native structure at very high temperatures (\u3e70 °C) for extended periods of time. Significant changes in either structure or backbone dynamics between 25 and 70 °C are not apparent for either protein. A kinetic difference with respect to metal loss is observed as in previous studies, but the extreme stability of both proteins in the presence of metal makes thermodynamic differences difficult to monitor. In the absence of metal, however, a largely reversible thermal denaturation can be monitored, and a comparison of the two apoproteins can offer insights into the origin of stability. Below denaturation temperatures apo-PfRd is found to have a structure nearly identical to that of the native holo form, except immediately adjacent to the metal binding site. In contrast, apo-CpRd is found to have a structure distinctly different from that of its holo form at low temperatures. This structure is rapidly lost upon heating, unfolding at approximately 40 °C. A PfRd mutant with the hydrophobic core mutated to match that of CpRd shows no change in thermostability in the metal-free state. A metal-free chimera with residues 1-15 of CpRd and the remaining 38 residues of PfRd is severely destabilized and is unfolded at 25 °C. Hence, the hydrophobic core does not seem to be the key determinant of thermostability; instead, data point to the hydrogen bond network centered on the first 15 residues or the interaction of these 15 residues with other parts of the protein as a possible contributor to the thermostability

Evidence for selenocysteine coordination to the active site nickel in the [NiFeSe]hydrogenases from Desulfovibrio baculatus.

Ni and Se x-ray absorption spectroscopic studies of the [NiFeSe]hydrogenases from Desulfovibrio baculatus are described. The Ni site geometry is pseudo-octahedral with a coordinating ligand composition of 3-4 (N,O) at 2.06 A, 1-2 (S,Cl) at 2.17 A, and 1 Se at 2.44 A. The Se coordination environment consists of 1 C at 2.0 A and a heavy scatterer M (M = Ni or Fe) at approximately 2.4 A. These results are interpreted in terms of a selenocysteine residue coordinated to the Ni site. The possible role of the Ni-Se site in the catalytic activation of H2 is discussed