scholarly journals Asymmetric molecular architecture of the human γ-tubulin ring complex

2019 ◽  
Author(s):  
Michal Wieczorek ◽  
Linas Urnavicius ◽  
Shih-Chieh Ti ◽  
Kelly R. Molloy ◽  
Brian T. Chait ◽  
...  
Keyword(s):  
High Resolution ◽  
Structural Models ◽  
Structural Data ◽  
Molecular Architecture ◽  
Regulatory Factors ◽  
Ring Complex ◽  
Microtubule Formation ◽  
Helical Geometry ◽  
Helical Turn

SUMMARYThe γ-tubulin ring complex (γ-TuRC) is an essential regulator of centrosomal and acentrosomal microtubule formation 1–4. Metazoan γ-TuRCs isolate as ∼2 MDa complexes containing the conserved proteins γ-tubulin, GCP2 and GCP3, as well as the expanded subunits GCP4, GCP5, and GCP6 3,5,6. However, in current structural models, γ-TuRCs assemble solely from subcomplexes of γ-tubulin, GCP2 and GCP3 7. The role of the metazoan-specific subunits in γ-TuRC assembly and architecture are not currently known, due to a lack of high resolution structural data for the native complex. Here, we present a cryo-EM structure of the native human γ-TuRC at 3.8Å resolution. Our reconstruction reveals an asymmetric, single helical-turn and cone-shaped structure built from at least 34 polypeptides. Pseudo-atomic models indicate that GCP4, GCP5 and GCP6 form distinct Y-shaped assemblies that structurally mimic GCP2/GCP3 subcomplexes and are distal to the γ-TuRC “seam”. Evolutionary expansion in metazoan-specific subunits diversifies the γ-TuRC by introducing large (>100,000 Å2) surfaces that could interact with different regulatory factors. We also identify an unanticipated structural bridge that includes an actin-like protein and spans the γ-TuRC lumen. Despite its asymmetric composition and architecture, the human γ-TuRC arranges γ-tubulins into a helical geometry poised to nucleate microtubules. The observed compositional complexity of the γ-TuRC could self-regulate its assembly into a cone-shaped structure to control microtubule formation across diverse contexts, e.g. within biological condensates 8 or alongside existing filaments 9.

scholarly journals PyXlinkViewer: a flexible tool for visualisation of protein chemical crosslinking data within the PyMOL molecular graphics system

2020 ◽  
Author(s):  
Bob Schiffrin ◽  
Sheena. E. Radford ◽  
David. J. Brockwell ◽  
Antonio N. Calabrese
Keyword(s):  
High Resolution ◽  
Protein Structures ◽  
Structural Models ◽  
Structural Data ◽  
Chemical Crosslinking ◽  
Molecular Graphics ◽  
Flexible Tool ◽  
Dead End ◽  
Spacer Arm ◽  
User Friendly

AbstractChemical crosslinking-mass spectrometry (XL-MS) is a valuable technique for gaining insights into protein structure and the organization of macromolecular complexes. XL-MS data yields inter-residue restraints that can be compared with high-resolution structural data. Distances greater than the crosslinker spacer-arm can reveal lowly-populated “excited” states of proteins/protein assemblies, or crosslinks can be used as restraints to generate structural models in the absence of structural data. Despite increasing uptake of XL-MS, there are few tools to enable rapid and facile mapping of XL-MS data onto high-resolution structures or structural models. PyXlinkViewer is a user-friendly plugin for PyMOL v2 that maps intra-protein, inter-protein and dead-end crosslinks onto protein structures/models and automates the calculation of inter-residue distances for the detected crosslinks. This enables rapid visualisation of XL-MS data, assessment of whether a set of detected crosslinks is congruent with structural data, and easy production of high-quality images for publication.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

HRTEM study of valleriite, a hydroxide-bearing copper sulfide

1990 ◽  
Vol 48 (4) ◽  
pp. 462-463
Author(s):  
S. Wang ◽  
P. R. Buseck
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Copper Sulfide ◽  
Carbonaceous Chondrite ◽  
Structural Data ◽  
Basic Structure ◽  
Long Period ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Wavy Structure

Valleriite is an unusual mineral, consisting of intergrowths of sulfide layers (corresponding in structure to the mineral smythite - Fe9S11) and hydroxide layers (corresponding to brucite - Mg(OH2)). It has a composition of approximately 1.526[Mg.68Al.32(OH)2].[Fe1.07Cu.93S2] and consists of two interpenetrating lattices, each of which retains its individual structural and diffraction characteristics parallel to the layering. The valleriite structure is related to that of tochilinite, an unusual iron-rich mineral that is of considerable interest for the origin of certain carbonaceous chondrite meteorites and to those of franckeite and cylindrite, two minerals that are of interest because of their unique morphological and crystallographic properties, e.g., the distinctive curved form of cylindrite and the perfect mica-like cleavage with unusual striations and the long-period wavy structure of franckeite.Our selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscope (HRTEM) images of valleriite provide new structural data. A basic structure and a new superstructure have been observed.

Quantitative accuracy of serotonergic neurotrans-mission imaging with high-resolution 123I SPECT

2004 ◽  
Vol 43 (06) ◽  
pp. 185-189 ◽  
Author(s):  
J. T. Kuikka
Keyword(s):  
High Resolution ◽  
Scatter Correction ◽  
Region Of Interest ◽  
Binding Potential ◽  
Partial Volume ◽  
Therapeutic Drugs ◽  
Quantitative Accuracy ◽  
Critical Error ◽  
Statistical Noise

Summary Aim: Serotonin transporter (SERT) imaging can be used to study the role of regional abnormalities of neurotransmitter release in various mental disorders and to study the mechanism of action of therapeutic drugs or drugs’ abuse. We examine the quantitative accuracy and reproducibility that can be achieved with high-resolution SPECT of serotonergic neurotransmission. Method: Binding potential (BP) of 123I labeled tracer specific for midbrain SERT was assessed in 20 healthy persons. The effects of scatter, attenuation, partial volume, mis-registration and statistical noise were estimated using phantom and human studies. Results: Without any correction, BP was underestimated by 73%. The partial volume error was the major component in this underestimation whereas the most critical error for the reproducibility was misplacement of region of interest (ROI). Conclusion: The proper ROI registration, the use of the multiple head gamma camera with transmission based scatter correction introduce more relevant results. However, due to the small dimensions of the midbrain SERT structures and poor spatial resolution of SPECT, the improvement without the partial volume correction is not great enough to restore the estimate of BP to that of the true one.

Which is the role of dynamic high-resolution ultrasound (D-HRUS) in the assessment of plantar plate tears?

2008 ◽  
Vol 29 (S 1) ◽  
Author(s):  
LM Sconfienza ◽  
F Lacelli ◽  
G Grillo ◽  
G Serafini ◽  
G Garlaschi ◽  
...  
Keyword(s):  
High Resolution ◽  
Plantar Plate

High-Resolution CT in Paraquat Poisoning of the Lung: Role of Prognosis Prediction

1998 ◽  
Vol 38 (6) ◽  
pp. 1027
Author(s):  
Kyoung Suk Kim ◽  
Young Tong Kim ◽  
Eun Joo Kwon ◽  
Choung Sik Choi ◽  
Han Heag Im ◽  
...  
Keyword(s):  
High Resolution ◽  
Prognosis Prediction ◽  
High Resolution Ct ◽  
Paraquat Poisoning

scholarly journals The Role of High-Resolution Analytical Techniques in the Development of Functional Foods

2021 ◽  
Vol 22 (6) ◽  
pp. 3220
Author(s):  
Álvaro Fernández-Ochoa ◽  
Francisco Javier Leyva-Jiménez ◽  
María De la Luz Cádiz-Gurrea ◽  
Sandra Pimentel-Moral ◽  
Antonio Segura-Carretero
Keyword(s):  
High Resolution ◽  
Functional Foods ◽  
Intervention Studies ◽  
Analytical Techniques ◽  
Nutritional Intervention ◽  
Bioactive Properties ◽  
Metabolic Reactions ◽  
Bioactive Potential ◽  
Endogenous Metabolites

The approaches based on high-resolution analytical techniques, such as nuclear magnetic resonance or mass spectrometry coupled to chromatographic techniques, have a determining role in several of the stages necessary for the development of functional foods. The analyses of botanical extracts rich in bioactive compounds is one of the fundamental steps in order to identify and quantify their phytochemical composition. However, the compounds characterized in the extracts are not always responsible for the bioactive properties because they generally undergo metabolic reactions before reaching the therapeutic targets. For this reason, analytical techniques are also applied to analyze biological samples to know the bioavailability, pharmacokinetics and/or metabolism of the compounds ingested by animal or human models in nutritional intervention studies. In addition, these studies have also been applied to determine changes of endogenous metabolites caused by prolonged intake of compounds with bioactive potential. This review aims to describe the main types and modes of application of high-resolution analytical techniques in all these steps for functional food development.

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