Energy Transducing Roles of Antiporter-like Subunits in Escherichia coli NDH-1 with Main Focus on Subunit NuoN (ND2)

The proton-translocating NADH-quinone oxidoreductase (complex I/NDH-1) contains a peripheral and a membrane domain. Three antiporter-like subunits in the membrane domain, NuoL, NuoM, and NuoN (ND5, ND4 and ND2, respectively), are structurally similar. We analyzed the role of NuoN in Escherichia coli NDH-1. The lysine residue at position 395 in NuoN (NLys(395)) is conserved in NuoL (LLys(399)) but is replaced by glutamic acid (MGlu(407)) in NuoM. Our mutation study on NLys(395) suggests that this residue participates in the proton translocation. Furthermore, we found that MGlu(407) is also essential and most likely interacts with conserved LArg(175). Glutamic acids, NGlu(133), MGlu(144), and LGlu(144), are corresponding residues. Unlike mutants of MGlu(144) and LGlu(144), mutation of NGlu(133) scarcely affected the energy-transducing activities. However, a double mutant of NGlu(133) and nearby KGlu(72) showed significant inhibition of these activities. This suggests that NGlu(133) bears a functional role similar to LGlu(144) and MGlu(144) but its mutation can be partially compensated by the nearby carboxyl residue. Conserved prolines located at loops of discontinuous transmembrane helices of NuoL, NuoM, and NuoN were shown to play a similar role in the energy-transducing activity. It seems likely that NuoL, NuoM, and NuoN pump protons by a similar mechanism. Our data also revealed that NLys(158) is one of the key interaction points with helix HL in NuoL. A truncation study indicated that the C-terminal amphipathic segments of NTM14 interacts with the Mβ sheet located on the opposite side of helix HL. Taken together, the mechanism of H(+) translocation in NDH-1 is discussed.

Crystal Structure of Anti-polysialic Acid Antibody Single Chain Fv Fragment Complexed with Octasialic Acid

Polysialic acid is a linear homopolymer of α2-8-linked sialic acids attached mainly onto glycoproteins. Cell surface polysialic acid plays roles in cell adhesion and differentiation events in a manner that is often dependent on the degree of polymerization (DP). Anti-oligo/polysialic acid antibodies have DP-dependent antigenic specificity, and such antibodies are widely utilized in biological studies for detecting and distinguishing between different oligo/polysialic acids. A murine monoclonal antibody mAb735 has a unique preference for longer polymers of polysialic acid (DP >10), yet the mechanism of recognition at the atomic level remains unclear. Here, we report the crystal structure of mAb735 single chain variable fragment (scFv735) in complex with octasialic acid at 1.8 Å resolution. In the asymmetric unit, two scFv735 molecules associate with one octasialic acid. In both complexes of the unit, all the complementarity-determining regions except for L3 interact with three consecutive sialic acid residues out of the eight. A striking feature of the complex is that 11 ordered water molecules bridge the gap between antibody and ligand, whereas the direct antibody-ligand interaction is less extensive. The dihedral angles of the trisialic acid unit directly interacting with scFv735 are not uniform, indicating that mAb735 does not strictly favor the previously proposed helical conformation. Importantly, both reducing and nonreducing ends of the bound ligand are completely exposed to solvent. We suggest that mAb735 gains its apparent high affinity for a longer polysialic acid chain by recognizing every three sialic acid units in a paired manner.

Recognition of Bisecting N-Acetylglucosamine

Dendritic cell inhibitory receptor 2 (DCIR2) is a C-type lectin expressed on classical dendritic cells. We recently identified the unique ligand specificity of mouse DCIR2 (mDCIR2) toward biantennary complex-type glycans containing bisecting N-acetylglucosamine (GlcNAc). Here, we report the crystal structures of the mDCIR2 carbohydrate recognition domain in unliganded form as well as in complex with an agalactosylated complex-type N-glycan unit carrying a bisecting GlcNAc residue. Bisecting GlcNAc and the α1-3 branch of the biantennary oligosaccharide asymmetrically interact with canonical and non-canonical mDCIR2 residues. Ligand-protein interactions occur directly through mDCIR2-characteristic amino acid residues as well as via a calcium ion and water molecule. Our structural and biochemical data elucidate for the first time the unique binding mode of mDCIR2 for bisecting GlcNAc-containing glycans, a mode that contrasts sharply with that of other immune C-type lectin receptors such as DC-SIGN.

New records ofLaboulbenia(Fungi, Ascomycota) from Ecuador and other countries

Communicating across generations: The Bsisterlanguage

Bsister proteins form a clade of MADS-box transcription factors that originated 300 million years ago, after ferns diverged but before Angiosperms and Gymnosperms lineages did. Thus, Bsister proteins have been found in both Gymnosperm and Angiosperm species such as paddy oat (Gnetum gnemon), ginkgo, yew (Taxus baccata), rape seed, rice, maize, wheat, petunia, snapdragon, tomato and Arabidopsis. In all these species, they are expressed in female reproductive organs.\udIn this review we go over the evolution and pattern of expression of the Bsister proteins, and we have a glance on their interaction patterns in the form of high order MADS-box complexes in different species. We describe the functions that have been assigned to them according to the analysis of mutants and RNA interference data. We finish this review discussing from a novel point of view the role that Bsister proteins might have, also in tetramer combinations with other MADS-box proteins, on the regulation of tissues communication occurring during reproduction. It is known that a cross-talk is essential for a proper ovule and seed development and Bsister and their target genes might play key roles in these communication processes

Convergence to the Time Average by Stochastic Regularization

In Ergodic Theory it is natural to consider the pointwise convergence of finite time averages of functions with respect to the flow of dynamical systems. Since the pointwise convergence is too weak for applications to Hamiltonian Perturbation Theory, requiring differentiability, we first introduce regularized averages obtained through a stochastic perturbation of an integrable Hamiltonian flow, and then we provide detailed estimates. In particular, for a special vanishing limit of the stochastic perturbation, we obtain convergence even in a Sobolev norm taking into account the derivatives

Genetics of a Lessepsian sprinter: the bluespotted cornetfish, Fistularia commersonii

Our current understanding of the mechanisms that lead to successful biological invasions is limited. Although local adaptation plays a central role in biological invasions, genetic studies have failed to produce a unified theory so far. The bluespotted cornetfish, a recent invader of the Mediterranean Sea from the Red Sea via the Suez Canal, provides an ideal case study to research the mechanisms of invasive genetics. Previous genetic work based on mitochondrial markers has shown the genetic diversity of the Mediterranean population was greatly reduced in comparison to the natural population in the Red Sea. In the current study, we expand upon these studies by adding mitochondrial and nuclear markers. Mitochondrial results confirm previous findings. The nuclear marker, however, does not show evidence of reduction in diversity. We interpret these results as either a differential dispersal capability in males and females, or the presence of selection on the invading Mediterranean population.

The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey

We present the design and performance of the multi-object fiber spectrographsfor the Sloan Digital Sky Survey (SDSS) and their upgrade for the BaryonOscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, thespectrographs produced more than 1.5 million spectra for the SDSS and SDSS-IIsurveys, enabling a wide variety of Galactic and extra-galactic scienceincluding the first observation of baryon acoustic oscillations in 2005. Thespectrographs were upgraded in 2009 and are currently in use for BOSS, theflagship survey of the third-generation SDSS-III project. BOSS will measureredshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alphaabsorption of 160,000 high redshift quasars over 10,000 square degrees of sky,making percent level measurements of the absolute cosmic distance scale of theUniverse and placing tight constraints on the equation of state of dark energy. The twin multi-object fiber spectrographs utilize a simple optical layoutwith reflective collimators, gratings, all-refractive cameras, andstate-of-the-art CCD detectors to produce hundreds of spectra simultaneously intwo channels over a bandpass covering the near ultraviolet to the nearinfrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on provenheritage, the spectrographs were upgraded for BOSS with volume-phaseholographic gratings and modern CCD detectors, improving the peak throughput bynearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000nm, and increasing the number of fibers from 640 to 1000 per exposure. In thispaper we describe the original SDSS spectrograph design and the upgradesimplemented for BOSS, and document the predicted and measured performances.

On the detection and tracking of space debris using the Murchison Widefield Array. I. Simulations and test observations demonstrate feasibility

The Murchison Widefield Array (MWA) is a new low frequency interferomericradio telescope. The MWA is the low frequency precursor to the Square KilometreArray (SKA) and is the first of three SKA precursors to be operational,supporting a varied science mission ranging from the attempted detection of theEpoch of Reionisation to the monitoring of solar flares and space weather. Weexplore the possibility that the MWA can be used for the purposes of SpaceSituational Awareness (SSA). In particular we propose that the MWA can be usedas an element of a passive radar facility operating in the frequency range 87.5- 108 MHz (the commercial FM broadcast band). In this scenario the MWA can beconsidered the receiving element in a bi-static radar configuration, with FMbroadcast stations serving as non-cooperative transmitters. The FM broadcastspropagate into space, are reflected off debris in Earth orbit, and are receivedat the MWA. The imaging capabilities of the MWA can be used to simultaneouslydetect multiple pieces of space debris, image their positions on the sky as afunction of time, and provide tracking data that can be used to determineorbital parameters. Such a capability would be a valuable addition toAustralian and global SSA assets, in terms of southern and eastern hemisphericcoverage. We provide a feasibility assessment of this proposal, based on simplecalculations and electromagnetic simulations that shows the detection ofsub-metre size debris should be possible (debris radius of >0.5 m to ~1000 kmaltitude). We also present a proof-of-concept set of observations thatdemonstrate the feasibility of the proposal, based on the detection andtracking of the International Space Station via reflected FM broadcast signalsoriginating in south-west Western Australia. These observations broadlyvalidate our calculations and simulations.

A 189 MHz, 2400 square degree polarization survey with the Murchison Widefield Array 32-element prototype

We present a Stokes I, Q and U survey at 189 MHz with the Murchison WidefieldArray 32-element prototype covering 2400 square degrees. The survey has a 15.6arcmin angular resolution and achieves a noise level of 15 mJy/beam. Wedemonstrate a novel interferometric data analysis that involves calibration ofdrift scan data, integration through the co-addition of warped snapshot imagesand deconvolution of the point spread function through forward modeling. Wepresent a point source catalogue down to a flux limit of 4 Jy. We detectpolarization from only one of the sources, PMN J0351-2744, at a level of 1.8\pm 0.4%, whereas the remaining sources have a polarization fraction below 2%.Compared to a reported average value of 7% at 1.4 GHz, the polarizationfraction of compact sources significantly decreases at low frequencies. We finda wealth of diffuse polarized emission across a large area of the survey with amaximum peak of ~13 K, primarily with positive rotation measure values smallerthan +10 rad/m^2. The small values observed indicate that the emission islikely to have a local origin (closer than a few hundred parsecs). There is alarge sky area at 2^h30^m where the diffuse polarized emission rms is fainterthan 1 K. Within this area of low Galactic polarization we characterize theforeground properties in a cold sky patch at $(\alpha,\delta) =(4^h,-27^\circ.6)$ in terms of three dimensional power spectra