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Yoshinori Satow - One of the best experts on this subject based on the ideXlab platform.

  • Crystal Twinning of human md 2 recognizing endotoxin cores of lipopolysaccharide
    Journal of Synchrotron Radiation, 2008
    Co-Authors: Umeharu Ohto, Yoshinori Satow
    Abstract:

    Twinning of Crystals causes overlapping of two or more reciprocal lattice points, and hence structure amplitudes for a single Crystalline domain are hardly obtained from X-ray diffraction intensities. MD-2 protein forms a stable complex with Toll-like receptor 4 and recognizes bacterial lipopolysaccharide (LPS). Excessive immune responses activated by LPS cause septic shocks. Saccharide-trimmed human MD-2 Crystallizes in the tetragonal form with apparent Laue symmetry of 4/mmm, and diffraction intensities from these Crystals indicate Crystal Twinning. The Crystal consists of two different domains, A and B. The cA axis of domain A coincides with the cB axis of domain B with a smaller lattice, and the aA axis corresponds to the (aB + bB) axis. This Twinning severely imposes difficulty in structure determination. Through optimization of cryoprotectant, domain A was thoroughly transformed into domain B. The Crystal containing only domain B is in space group P41212 with one MD-2 molecule in the asymmetric unit. The structure of this form of MD-2 as well as its complex with antiendotoxic lipid IVa was successfully determined using the multiple isomorphous replacement method.

  • endotoxin cores of lipopolysaccharide
    2007
    Co-Authors: Umeharu Ohto, Yoshinori Satow
    Abstract:

    Twinning of Crystals causes overlapping of two or more reciprocal lattice points, and hence structure amplitudes for a single Crystalline domain are hardly obtained from X-ray diffraction intensities. MD-2 protein forms a stable complex with Toll-like receptor 4 and recognizes bacterial lipopolysaccharide (LPS). Excessive immune responses activated by LPS cause septic shocks. Saccharide-trimmed human MD-2 Crystallizes in the tetragonal form with apparent Laue symmetry of 4/mmm, and diffraction intensities from these Crystals indicate Crystal Twinning. The Crystal consists of two different domains, A and B. The cA axis of domain A coincides with the cB axis of domain B with a smaller lattice, and the aA axis corresponds to the (aB + bB) axis. This Twinning severely imposes difficulty in structure determination. Through optimization of cryoprotectant, domain A was thoroughly transformed into domain B. The Crystal containing only domain B is in space group P41212 with one MD-2 molecule in the asymmetric unit. The structure of this form of MD-2 as well as its complex with antiendotoxic lipid IVa was successfully determined using the multiple isomorphous replacement method

Todd O Yeates - One of the best experts on this subject based on the ideXlab platform.

  • detecting and overcoming Crystal Twinning
    Methods in Enzymology, 1997
    Co-Authors: Todd O Yeates
    Abstract:

    Twinning is fairly common in protein Crystals. In its merohedral from, Twinning is not apparent in the diffraction pattern, but the observed intensities do not represent individual Crystallographic intensities. Since partial Twinning (twin fraction less than 1/2) and perfect Twinning (twin fraction of 1/2) can both be identified relatively easily by examining intensity statistics, the appropriate tests should be performed routinely when working in space groups that support merohedral Twinning.

  • 22 detecting and overcoming Crystal Twinning
    Methods in Enzymology, 1997
    Co-Authors: Todd O Yeates
    Abstract:

    Twinning is fairly common in protein Crystals. In its merohedral from, Twinning is not apparent in the diffraction pattern, but the observed intensities do not represent individual Crystallographic intensities. Since partial Twinning (twin fraction less than 1/2) and perfect Twinning (twin fraction of 1/2) can both be identified relatively easily by examining intensity statistics, the appropriate tests should be performed routinely when working in space groups that support merohedral Twinning.

John R. Helliwell - One of the best experts on this subject based on the ideXlab platform.

  • macromolecular Crystal Twinning lattice disorders and multiple Crystals
    Crystallography Reviews, 2008
    Co-Authors: John R. Helliwell
    Abstract:

    Macromolecule Crystal structure analyses can be severely hampered by cases of Twinning or of lattice disorders or of multiple Crystals. However, it is increasingly the case that Twinning can readily be recognized and accounted for, or remediations found. A review of this topic is given, covering both the less-than-perfect and perfect Twinning situations. Remediation of Twinning cases is possible via alteration of Crystal growth conditions including use, mainly, of chemical additives. The case of multiple Crystal growths likewise can hamper Crystal structure analysis and, although not necessarily associated with Twinning, is a Crystal growth situation where similar remediation methods are adopted. There is a nice body of case studies now in the Crystallographic literature about macromolecule Crystal Twinning and multiple Crystals situations that make it timely to write this review. The literature on other macromolecule Crystal disorders is much smaller but include incommensurate superlattice effects, which...

Massimo Nespolo - One of the best experts on this subject based on the ideXlab platform.

Dickson, Veronica Kane - One of the best experts on this subject based on the ideXlab platform.

  • Phasing and structure of Bestrophin-1; a case study in the use of heavy atom cluster compounds with multi-subunit transmembrane proteins
    Acta Crystallographica Section D: Structural Biology, 2016
    Co-Authors: Dickson, Veronica Kane
    Abstract:

    The purification and three-dimensional Crystallisation of membrane proteins are commonly affected by a cumulation of pathologies that are less prevalent in their soluble counterparts. This may include severe anisotropy, poor spot shape, poor to moderate resolution diffraction, Crystal Twinning, translational pseudo-symmetry, and poor uptake of heavy atoms for derivatisation. Such challenges must be circumvented by adaptations in the approach to Crystallisation and/or phasing. Here we present an example of a protein that exhibited all of the above-mentioned complications. Bestrophin-1 is a eukaryotic calciumactivated chloride channel, the structure of which was recently determined in complex with monoclonal antibody fragments using SAD phasing with tantalum bromide clusters (Ta6Br12·Br2). We discuss some of the obstacles to obtaining improved diffraction and phasing for this particular channel, as well as the approach and adaptations that were key to determining the structure.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the International Union of Crystallography