Crystallographic study of the 2-thioribothymidine-synthetic complex TtuA–TtuB fromThermus thermophilus

The ubiquitin-like protein TtuB is a sulfur carrier for the biosynthesis of 2-thioribothymidine (s2T) at position 54 in some thermophilic bacterial tRNAs. TtuB captures a S atom at its C-terminus as a thiocarboxylate and transfers it to tRNA by the transferase activity of TtuA. TtuB also functions to suppress s2T formation by forming a covalent bond with TtuA. To explore how TtuB interacts with TtuA and switches between these two different functions, high-resolution structure analysis of the TtuA–TtuB complex is required. In this study, the TtuA–TtuB complex fromThermus thermophiluswas expressed, purified and crystallized. To mimic the thiocarboxylated TtuB, the C-terminal Gly residue was replaced with Cys (G65C) to obtain crystals of the TtuA–TtuB complex. A Zn-MAD data set was collected to a resolution of 2.5 Å. MAD analysis successfully determined eight Zn sites, and a partial structure model composed of four TtuA–TtuB complexes in the asymmetric unit was constructed.

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High Resolution Structure of the ba3 Cytochrome c Oxidase from Thermus thermophilus in a Lipidic Environment

PLoS ONE ◽

10.1371/journal.pone.0022348 ◽

2011 ◽

Vol 6 (7) ◽

pp. e22348 ◽

Cited By ~ 81

Author(s):

Theresa Tiefenbrunn ◽

Wei Liu ◽

Ying Chen ◽

Vsevolod Katritch ◽

C. David Stout ◽

...

Keyword(s):

High Resolution ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Thermus Thermophilus ◽

High Resolution Structure ◽

Resolution Structure

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Structure of a Tc holotoxin pore provides insights into the translocation mechanism

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1909821116 ◽

2019 ◽

Vol 116 (46) ◽

pp. 23083-23090 ◽

Cited By ~ 7

Author(s):

Daniel Roderer ◽

Oliver Hofnagel ◽

Roland Benz ◽

Stefan Raunser

Keyword(s):

Pathogenic Bacteria ◽

Conformational Transition ◽

Target Cells ◽

Photorhabdus Luminescens ◽

C Terminus ◽

Head Groups ◽

Toxin Complex ◽

High Resolution Structure ◽

Translocation Mechanism ◽

Resolution Structure

Tc toxins are modular toxin systems of insect and human pathogenic bacteria. They are composed of a 1.4-MDa pentameric membrane translocator (TcA) and a 250-kDa cocoon (TcB and TcC) encapsulating the 30-kDa toxic enzyme (C terminus of TcC). Binding of Tc toxins to target cells and a pH shift trigger the conformational transition from the soluble prepore state to the membrane-embedded pore. Subsequently, the toxic enzyme is translocated and released into the cytoplasm. A high-resolution structure of a holotoxin embedded in membranes is missing, leaving open the question of whether TcB-TcC has an influence on the conformational transition of TcA. Here we show in atomic detail a fully assembled 1.7-MDa Tc holotoxin complex from Photorhabdus luminescens in the membrane. We find that the 5 TcA protomers conformationally adapt to fit around the cocoon during the prepore-to-pore transition. The architecture of the Tc toxin complex allows TcB-TcC to bind to an already membrane-embedded TcA pore to form a holotoxin. Importantly, assembly of the holotoxin at the membrane results in spontaneous translocation of the toxic enzyme, indicating that this process is not driven by a proton gradient or other energy source. Mammalian lipids with zwitterionic head groups are preferred over other lipids for the integration of Tc toxins. In a nontoxic Tc toxin variant, we can visualize part of the translocating toxic enzyme, which transiently interacts with alternating negative charges and hydrophobic stretches of the translocation channel, providing insights into the mechanism of action of Tc toxins.

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High-resolution structure determination by ALCHEMI

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074707 ◽

1983 ◽

Vol 41 ◽

pp. 178-181 ◽

Cited By ~ 1

Author(s):

Peter G. Self ◽

Peter R. Buseck

Keyword(s):

Site Occupancy ◽

Real Space ◽

Unit Cell ◽

Bragg Angle ◽

Electron Current ◽

High Resolution Structure ◽

Beam Incident ◽

Crystallographic Planes ◽

Electron Beam Incident ◽

Resolution Structure

ALCHEMI (Atom Location by CHanneling Enhanced Microanalysis) enables the site occupancy of atoms in single crystals to be determined. In this article the fundamentals of the method for both EDS and EELS will be discussed. Unlike HRTEM, ALCHEMI does not place stringent resolution requirements on the microscope and, because EDS clearly distinguishes between elements of similar atomic number, it can offer some advantages over HRTEM. It does however, place certain constraints on the crystal. These constraints are: a) the sites of interest must lie on alternate crystallographic planes, b) the projected charge density on the alternate planes must be significantly different, and c) there must be at least one atomic species that lies solely on one of the planes.An electron beam incident on a crystal undergoes elastic scattering; in reciprocal space this is seen as a diffraction pattern and in real space this is a modulation of the electron current across the unit cell. When diffraction is strong (i.e., when the crystal is oriented near to the Bragg angle of a low-order reflection) the electron current at one point in the unit cell will differ significantly from that at another point.

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Cathodoluminescence of Catalyst Crystallites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055667 ◽

1982 ◽

Vol 40 ◽

pp. 664-665

Author(s):

E.D. Boyes ◽

P.L. Gai ◽

D.B. Darby ◽

C. Warwick

Keyword(s):

Defect Density ◽

Chemical Properties ◽

Operating Conditions ◽

Semiconductor Materials ◽

Environmental Cell ◽

High Resolution Structure ◽

Commercially Important ◽

Crystallographic Defects ◽

Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

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