Journal of Structural Biology

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  • Imaging Drosophila brain by combining cryo-soft X-ray microscopy of thick vitreous sections and cryo-electron microscopy of ultrathin vitreous sections
    [Oct 2014]

    Publication date: Available online 6 October 2014
    Source:Journal of Structural Biology

    Author(s): Amélie Leforestier , Pierre Levitz , Thomas Préat , Peter Guttmann , Laurent J. Michot , Paul Tchenio

    Cryo-soft X-ray microscopy is an emerging imaging tool complementary to cryo-electron microscopy, allowing to image frozen hydrated specimens ten to hundred times thicker, but at lower resolution. We describe how the method, so far restricted to isolated small cells or cell monolayers, can be extended to large cells and tissue. We image the synapses of the Kenyon cells in frozen hydrated Drosophila brains combining cryo-soft X-ray microscopy of thick vitreous sections, and cryo-electron microscopy of ultrathin vitreous sections. We show how to obtain frozen hydrated sections of thicknesses ranging from 40nm up to 2.5μm, by tuning the sectioning speed of the cryo-microtome. A fluorescent stereo-microscope mounted on the cryo-microtome allowed us to target the regions of interest after GFP-labeling of synapses. Thick cryo-sections were imaged by cryo-soft X-ray microscopy at a resolution better than 25nm, while ultrathin cryo-sections of the same regions were explored in parallel at the nanometre level of resolution by cryo-electron microscopy.





    Categories: Journal Articles
  • Efficient cryoprotection of macromolecular crystals using vapor diffusion of volatile alcohols
    [Oct 2014]

    Publication date: Available online 5 October 2014
    Source:Journal of Structural Biology

    Author(s): Christopher Farley , Douglas H. Juers

    Macromolecular X-ray crystallography, usually done at cryogenic temperature to limit radiation damage, often requires liquid cryoprotective soaking that can be labor intensive and damaging to crystals. Here we describe a method for cryoprotection that uses vapor diffusion of volatile cryoprotective agents into loop-mounted crystals. The crystal is mounted into a vial containing a small volume of an alcohol-based cryosolution. After a short incubation with the looped crystal sitting in the cryosolution vapor, the crystal is transferred directly from the vial into the cooling medium. Effective for several different protein crystals, the approach obviates the need for liquid soaking and opens up a heretofore underutilized class of cryoprotective agents for macromolecular crystallography.





    Categories: Journal Articles
  • Super-sampling SART with ordered subsets
    [Oct 2014]

    Publication date: Available online 2 October 2014
    Source:Journal of Structural Biology

    Author(s): Michael Kunz , Achilleas S. Frangakis

    In tomography, the quality of the reconstruction is essential because the complete cascade of the subsequent analysis is based on it. To date, weighted back-projection (WBP) has been the most commonly used technique due to its versatility and performance in sub-tomogram averaging. Here we present super-sampling SART that is based on the simultaneous algebraic reconstruction technique. While algebraic reconstruction techniques typically produce better contrast and lately showed a significant improvement in terms of processing speed, sub-tomogram averages derived from those reconstructions were inferior in resolution compared to those derived from WBP data. Super-sampling SART, however, outperforms both in term of contrast and the resolution achieved in sub-tomogram averaging several other tested methods and in particular WBP. The main feature of super-sampling SART, as the name implies, is the super-sampling option – by which parameter-based up-sampling and down-sampling are used to reduce artifacts. In particular, the aliasing that is omnipresent in the reconstruction can be practically eliminated without a significant increase in the computational time. Furthermore, super-sampling SART reaches convergence within a single iteration, making the processing time comparable to WBP, and eliminating the ambiguity of parameter-controlled convergence times. We find that grouping of projections increases the contrast, while when projections are used individually the resolution can be maximized. Using sub-tomogram averaging of ribosomes as a test case, we show that super-sampling SART achieves equal or better sub-tomogram averaging results than WBP, which is of particular importance in cryo-electron tomography.





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  • Cover 2 - Editorial Board
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1









    Categories: Journal Articles
  • Table of Contents / barcode
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1









    Categories: Journal Articles
  • Function-related adaptations of ultrastructure, mineral phase distribution and mechanical properties in the incisive cuticle of mandibles of Porcellio scaber Latreille, 1804
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Julia Huber , Helge-Otto Fabritius , Erika Griesshaber , Andreas Ziegler

    In terrestrial isopods the mandibles consist of a corpus carrying strong muscle tissue, and a pars incisiva (PI) that cuts dry leaves into smaller ingestible pieces. We studied the cuticle of the PI of Porcellio scaber in order to understand region-dependent differences in its ultrastructure, composition, and the resulting mechanical properties, employing several microscopic and analytical techniques as well as nanoindentation experiments. The cuticle of the incisive tip is not mineralized and consists of an unusually thick epicuticle containing thin fibrils, two subjacent cuticular layers, and a central core containing fibrils of different orientation, either longitudinal or circumferential. A thick epicuticle of the middle region just behind the tip projects long epicuticular extensions into the subjacent endocuticle, likely to prevent delamination. A distinct exocuticular layer is lacking in the middle region. Most chitin–protein fibrils within the endocuticle are oriented in parallel pointing towards the tip. Surprisingly, the middle region is mineralized by amorphous calcium phosphate (ACP) only. Near the base, ACP is successively replaced by amorphous calcium carbonate and calcite is restricted to a distal layer in the base. At the transition between middle and base, the epicuticle forms a hybrid material containing fibrils of the exocuticle. Nanoindentation experiments reveal an increase of the stiffness and hardness from the tip towards the base and significantly higher values on transversal in comparison to longitudinal planes. The results suggest that ultrastructure and composition are adapted for conveying high forces from a rather thin cutting edge to the stable base of the PI.





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  • Repurposing TRASH: Emergence of the enzyme organomercurial lyase from a non-catalytic zinc finger scaffold
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Gurmeet Kaur , Srikrishna Subramanian

    The mercury resistance pathway enzyme organomercurial lyase (MerB) catalyzes the conversion of organomercurials to ionic mercury (Hg2+). Here, we provide evidence for the emergence of this enzyme from a TRASH-like, non-enzymatic, treble-clef zinc finger ancestor by domain duplication and fusion. Surprisingly, the structure-stabilizing metal-binding core of the treble-clef appears to have been repurposed in evolution to serve a catalytic role. Novel enzymatic functions are believed to have evolved from ancestral generalist catalytic scaffolds or from already specialized enzymes with catalytic promiscuity. The emergence of MerB from a zinc finger ancestor serves as a rare example of how a novel enzyme may emerge from a non-catalytic scaffold with a related binding function.





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  • Crystal structure of PhoU from Pseudomonas aeruginosa, a negative regulator of the Pho regulon
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Sang Jae Lee , Ye Seol Park , Soon-Jong Kim , Bong-Jin Lee , Se Won Suh

    In Escherichia coli, seven genes (pstS, pstC, pstA, pstB, phoU, phoR, and phoB) are involved in sensing environmental phosphate (Pi) and controlling the expression of the Pho regulon. PhoU is a negative regulator of the Pi-signaling pathway and modulates Pi transport through Pi transporter proteins (PstS, PstC, PstA, and PstB) through the two-component system PhoR and PhoB. Inactivation of PhoY2, one of the two PhoU homologs in Mycobacterium tuberculosis, causes defects in persistence phenotypes and increased susceptibility to antibiotics and stresses. Despite the important biological role, the mechanism of PhoU function is still unknown. Here we have determined the crystal structure of PhoU from Pseudomonas aeruginosa. It exists as a dimer in the crystal, with each monomer consisting of two structurally similar three-helix bundles. Our equilibrium sedimentation measurements support the reversible monomer–dimer equilibrium model in which P. aeruginosa PhoU exists in solution predominantly as dimers, with monomers in a minor fraction, at low protein concentrations. The dissociation constant for PhoU dimerization is 3.2×10−6 M. The overall structure of P. aeruginosa PhoU dimer resembles those of Aquifex aeolicus PhoU and Thermotoga maritima PhoU2. However, it shows distinct structural features in some loops and the dimerization pattern.





    Categories: Journal Articles
  • Single virus detection by means of atomic force microscopy in combination with advanced image analysis
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Thomas Bocklitz , Evelyn Kämmer , Stephan Stöckel , Dana Cialla-May , Karina Weber , Roland Zell , Volker Deckert , Jürgen Popp

    In the present contribution virions of five different virus species, namely Varicella-zoster virus, Porcine teschovirus, Tobacco mosaic virus, Coliphage M13 and Enterobacteria phage PsP3, are investigated using atomic force microscopy (AFM). From the resulting height images quantitative features like maximal height, area and volume of the viruses could be extracted and compared to reference values. Subsequently, these features were accompanied by image moments, which quantify the morphology of the virions. Both types of features could be utilized for an automatic discrimination of the five virus species. The accuracy of this classification model was 96.8%. Thus, a virus detection on a single-particle level using AFM images is possible. Due to the application of advanced image analysis the morphology could be quantified and used for further analysis. Here, an automatic recognition by means of a classification model could be achieved in a reliable and objective manner.





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  • Ocean acidification reduces the crystallographic control in juvenile mussel shells
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Susan C. Fitzer , Maggie Cusack , Vernon R. Phoenix , Nicholas A. Kamenos

    Global climate change threatens the oceans as anthropogenic carbon dioxide causes ocean acidification and reduced carbonate saturation. Future projections indicate under saturation of aragonite, and potentially calcite, in the oceans by 2100. Calcifying organisms are those most at risk from such ocean acidification, as carbonate is vital in the biomineralisation of their calcium carbonate protective shells. This study highlights the importance of multi-generational studies to investigate how marine organisms can potentially adapt to future projected global climate change. Mytilus edulis is an economically important marine calcifier vulnerable to decreasing carbonate saturation as their shells comprise two calcium carbonate polymorphs: aragonite and calcite. M. edulis specimens were cultured under current and projected pCO2 (380, 550, 750 and 1000μatm), following 6months of experimental culture, adults produced second generation juvenile mussels. Juvenile mussel shells were examined for structural and crystallographic orientation of aragonite and calcite. At 1000μatm pCO2, juvenile mussels spawned and grown under this high pCO2 do not produce aragonite which is more vulnerable to carbonate under-saturation than calcite. Calcite and aragonite were produced at 380, 550 and 750μatm pCO2. Electron back scatter diffraction analyses reveal less constraint in crystallographic orientation with increased pCO2. Shell formation is maintained, although the nacre crystals appear corroded and crystals are not so closely layered together. The differences in ultrastructure and crystallography in shells formed by juveniles spawned from adults in high pCO2 conditions may prove instrumental in their ability to survive ocean acidification.





    Categories: Journal Articles
  • Holoenzyme structures of endothelial nitric oxide synthase – An allosteric role for calmodulin in pivoting the FMN domain for electron transfer
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Niels Volkmann , Pavel Martásek , Linda J. Roman , Xiao-Ping Xu , Christopher Page , Mark Swift , Dorit Hanein , Bettie Sue Masters

    While the three-dimensional structures of heme- and flavin-binding domains of the NOS isoforms have been determined, the structures of the holoenzymes remained elusive. Application of electron cryo-microscopy and structural modeling of the bovine endothelial nitric oxide synthase (eNOS) holoenzyme produced detailed models of the intact holoenzyme in the presence and absence of Ca2+/calmodulin (CaM). These models accommodate the cross-electron transfer from the reductase in one monomer to the heme in the opposite monomer. The heme domain acts as the anchoring dimeric structure for the entire enzyme molecule, while the FMN domain is activated by CaM to move flexibly to bridge the distance between the reductase and oxygenase domains. Our results indicate that the key regulatory role of CaM involves the stabilization of structural intermediates and precise positioning of the pivot for the FMN domain tethered shuttling motion to accommodate efficient and rapid electron transfer in the homodimer of eNOS.





    Categories: Journal Articles
  • Nanoscale three-dimensional imaging of the human myocyte
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Matthew S. Sulkin , Fei Yang , Katherine M. Holzem , Brandon Van Leer , Cliff Bugge , Jacob I. Laughner , Karen Green , Igor R. Efimov

    The ventricular human myocyte is spatially organized for optimal ATP and Ca2+ delivery to sarcomeric myosin and ionic pumps during every excitation–contraction cycle. Comprehension of three-dimensional geometry of the tightly packed ultrastructure has been derived from discontinuous two-dimensional images, but has never been precisely reconstructed or analyzed in human myocardium. Using a focused ion beam scanning electron microscope, we created nanoscale resolution serial images to quantify the three-dimensional ultrastructure of a human left ventricular myocyte. Transverse tubules (t-tubule), lipid droplets, A-bands, and mitochondria occupy 1.8, 1.9, 10.8, and 27.9% of the myocyte volume, respectively. The complex t-tubule system has a small tortuosity (1.04±0.01), and is composed of long transverse segments with diameters of 317±24nm and short branches. Our data indicates that lipid droplets located well beneath the sarcolemma are proximal to t-tubules, where 59% (13 of 22) of lipid droplet centroids are within 0.50μm of a t-tubule. This spatial association could have an important implication in the development and treatment of heart failure because it connects two independently known pathophysiological alterations, a substrate switch from fatty acids to glucose and t-tubular derangement.





    Categories: Journal Articles
  • Visualisation by high resolution synchrotron X-ray phase contrast micro-tomography of gas films on submerged superhydrophobic leaves
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Torsten Lauridsen , Kyriaki Glavina , Timothy David Colmer , Anders Winkel , Sarah Irvine , Kim Lefmann , Robert Feidenhans’l , Ole Pedersen

    Floods can completely submerge terrestrial plants but some wetland species can sustain O2 and CO2 exchange with the environment via gas films forming on superhydrophobic leaf surfaces. We used high resolution synchrotron X-ray phase contrast micro-tomography in a novel approach to visualise gas films on submerged leaves of common cordgrass (Spartina anglica). 3D tomograms enabled a hitherto unmatched level of detail regarding the micro-topography of leaf gas films. Gas films formed only on the superhydrophobic adaxial leaf side (water droplet contact angle, Φ =162°) but not on the abaxial side (Φ =135°). The adaxial side of the leaves of common cordgrass is plicate with a longitudinal system of parallel grooves and ridges and the vast majority of the gas film volume was found in large ∼180μm deep elongated triangular volumes in the grooves and these volumes were connected to each neighbouring groove via a fine network of gas tubules (∼1.7μm diameter) across the ridges. In addition to the gas film retained on the leaf exterior, the X-ray phase contrast micro-tomography also successfully distinguished gas spaces internally in the leaf tissues, and the tissue porosity (gas volume per unit tissue volume) ranged from 6.3% to 20.3% in tip and base leaf segments, respectively. We conclude that X-ray phase contrast micro-tomography is a powerful tool to obtain quantitative data of exterior gas features on biological samples because of the significant difference in electron density between air, biological tissues and water.





    Categories: Journal Articles
  • Robust and low cost uniform 15N-labeling of proteins expressed in Drosophila S2 cells and Spodoptera frugiperda Sf9 cells for NMR applications
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Annalisa Meola , Célia Deville , Scott A. Jeffers , Pablo Guardado-Calvo , Ieva Vasiliauskaite , Christina Sizun , Christine Girard-Blanc , Christian Malosse , Carine van Heijenoort , Julia Chamot-Rooke , Thomas Krey , Eric Guittet , Stéphane Pêtres , Félix A. Rey , François Bontems

    Nuclear magnetic resonance spectroscopy is a powerful tool to study structural and functional properties of proteins, provided that they can be enriched in stable isotopes such as 15N, 13C and 2H. This is usually easy and inexpensive when the proteins are expressed in Escherichia coli, but many eukaryotic (human in particular) proteins cannot be produced this way. An alternative is to express them in insect cells. Labeled insect cell growth media are commercially available but at prohibitive prices, limiting the NMR studies to only a subset of biologically important proteins. Non-commercial solutions from academic institutions have been proposed, but none of them is really satisfying. We have developed a 15N-labeling procedure based on the use of a commercial medium depleted of all amino acids and supplemented with a 15N-labeled yeast autolysate for a total cost about five times lower than that of the currently available solutions. We have applied our procedure to the production of a non-polymerizable mutant of actin in Sf9 cells and of fragments of eukaryotic and viral membrane fusion proteins in S2 cells, which typically cannot be produced in E. coli, with production yields comparable to those obtained with standard commercial media. Our results support, in particular, the putative limits of a self-folding domain within a viral glycoprotein of unknown structure.





    Categories: Journal Articles
  • Dynamics of bovine opsin bound to G-protein fragments
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Minoru Sugihara , Makiko Suwa , Ana-Nicoleta Bondar

    G protein-coupled receptors (GPCRs) are a large class of membrane proteins that mediate communication of the cell with the outer environment. Upon activation by an agonist, GPCRs undergo large-scale conformational changes that enable binding of the G protein to the receptor. A key open question concerns the mechanism of the long-distance coupling between the agonist-binding site and the cytoplasmic site where G protein binds. Here we address this question by exploring the molecular dynamics of bovine opsin bound to three different fragments of G-proteins. We find that an extended network of hydrogen bonds connects the agonist retinal binding site to the G protein binding site via conserved amino acid residues. The dynamics of the hydrogen-bonding network inside opsin couples to interactions at the G protein binding site.





    Categories: Journal Articles
  • 2D and 3D crystallization of a bacterial homologue of human vitamin C membrane transport proteins
    [Oct 2014]

    Publication date: October 2014
    Source:Journal of Structural Biology, Volume 188, Issue 1

    Author(s): Jean-Marc Jeckelmann , Daniel Harder , Zöhre Ucurum , Dimitrios Fotiadis

    Most organisms are able to synthesize vitamin C whereas humans are not. In order to contribute to the elucidation of the molecular working mechanism of vitamin C transport through biological membranes, we cloned, overexpressed, purified, functionally characterized, and 2D- and 3D-crystallized a bacterial protein (UraDp) with 29% of amino acid sequence identity to the human sodium-dependent vitamin C transporter 1 (SVCT1). Ligand-binding experiments by scintillation proximity assay revealed that uracil is a substrate preferably bound to UraDp. For structural analysis, we report on the production of tubular 2D crystals and present a first projection structure of UraDp from negatively stained tubes. On the other hand the successful growth of UraDp 3D crystals and their crystallographic analysis is described. These 3D crystals, which diffract X-rays to 4.2Å resolution, pave the way towards the high-resolution crystal structure of a bacterial homologue with high amino acid sequence identity to human SVCT1.





    Categories: Journal Articles
  • Changes in tissue directionality reflect differences in myelin content after demyelination in mice spinal cords
    [Oct 2014]

    Publication date: Available online 1 October 2014
    Source:Journal of Structural Biology

    Author(s): Mohammad K. Ansari , Heather Y.F. Yong , Luanne Metz , V. Wee Yong , Yunyan Zhang

    Changes in myelin integrity are key manifestations of many neurological diseases including multiple sclerosis but precise measurement of myelin in vivo is challenging. The goal of this study was to evaluate myelin content in histological images obtained from a lysolecithin mouse model of demyelination, using a new quantitative method named structure tensor analysis. Injury was targeted at the dorsal column of mice spinal cords. We obtained 16 histological images stained with luxol fast blue for myelin from 9 mice: 9 images from lesion epicenter and 7 from a distant area 500-μm away from the epicenter. In each image, we categorized 3 tissue types: healthy, completely demyelinated, and partially demyelinated. Structure tensor analysis was applied to quantify the coherency (anisotropy), energy (trace of dominant directions), and angular entropy (degree of disorder) of each tissue. We found that completely demyelinated lesions had significantly lower coherency and energy but higher angular entropy than partially demyelinated and healthy tissues at both the epicenter and distant areas of the injury. In addition, the coherency of healthy tissue was greater than partially demyelinated tissue at each site. Within tissue category, we did not find differences in any measure between spinal cord locations. Our findings suggest that greater myelin integrity is associated with better tissue anisotropy, independent of injury location. Structure tensor analysis may serve as a new tool for quantitative measurement of myelin content in white matter, and this may help understand disease mechanisms and development in MS and other demyelinating disorders.





    Categories: Journal Articles
  • Near-atomic resolution reconstructions using a mid-range electron microscope operated at 200kV
    [Oct 2014]

    Publication date: Available online 30 September 2014
    Source:Journal of Structural Biology

    Author(s): Melody G. Campbell , Bradley M. Kearney , Anchi Cheng , Clinton S. Potter , John E. Johnson , Bridget Carragher , David Veesler

    A new era has begun for single particle cryo-electron microscopy (cryoEM) which can now compete with X-ray crystallography for determination of protein structures. The development of direct detectors constitutes a revolution that has led to a wave of near-atomic resolution cryoEM reconstructions. However, regardless of the sample studied, virtually all high-resolution reconstructions reported to date have been achieved using high-end microscopes. We demonstrate that the new generation of direct detectors coupled to a widely used mid-range electron microscope also enables obtaining cryoEM maps of sufficient quality for de novo modeling of protein structures of different sizes and symmetries. We provide an outline of the strategy used to achieve a 3.7Å resolution reconstruction of Nudaurelia capensis ω virus and a 4.2Å resolution reconstruction of the Thermoplasma acidophilum T20S proteasome.





    Categories: Journal Articles
  • Designability landscape reveals sequence features that define axial helix rotation in four-helical homo-oligomeric antiparallel coiled-coil structures
    [Oct 2014]

    Publication date: Available online 30 September 2014
    Source:Journal of Structural Biology

    Author(s): Krzysztof Szczepaniak , Grzegorz Lach , Janusz M. Bujnicki , Stanislaw Dunin-Horkawicz

    Coiled coils are widespread protein domains comprising α-helices wound around each other in a regular fashion. Owing to their regularity, coiled-coil structures can be fully described by parametric equations. This in turn makes them an excellent model for studying sequence–structure relationships in proteins. Here, we used computational design to identify sequence features that determine the degree of helix axial rotation in four-helical homo-oligomeric antiparallel coiled coils. We designed 135,000 artificial sequences for a repertoire of backbone models representing all theoretically possible axial rotation states. Analysis of the designed sequences revealed features that precisely define the rotation of the helices. Based on these features we implemented a bioinformatic tool, which given a coiled-coil sequence, predicts the rotation of the helices in its structure. Moreover, we showed that another structural parameter, helix axial shift, is coupled to helix axial rotation and that dependence between these two parameters narrows the number of possible axial rotation states.





    Categories: Journal Articles
  • Revisiting the NMR solution structure of the Cel48S type-I dockerin module from Clostridium thermocellum reveals a cohesin-primed conformation
    [Oct 2014]

    Publication date: Available online 28 September 2014
    Source:Journal of Structural Biology

    Author(s): Chao Chen , Zhenling Cui , Yan Xiao , Qiu Cui , Steven P. Smith , Raphael Lamed , Edward A. Bayer , Yingang Feng

    Dockerin modules of the cellulosomal enzyme subunits play an important role in the assembly of the cellulosome by binding tenaciously to cohesin modules of the scaffoldin subunit. A previously reported NMR-derived solution structure of the type-I dockerin module from Cel48S of Clostridium thermocellum, which utilized two-dimensional homonuclear 1H-1H NOESY and three-dimensional 15N-edited NOESY distance restraints, displayed substantial conformational differences from subsequent structures of dockerin modules in complex with their cognate cohesin modules, raising the question whether the source of the observed differences resulted from cohesin-induced structural rearrangements. Here, we determined the solution structure of the Cel48S type-I dockerin based on 15N- and 13C-edited NOESY-derived distance restraints. The structure adopted a fold similar to X-ray crystal structures of dockerin modules in complex with their cohesin partners. A unique cis-peptide bond between Leu-65 and Pro-66 in the Cel48S type-I dockerin module was also identified in the present structure. Our structural analysis of the Cel48S type-I dockerin module indicates that it does not undergo appreciable cohesin-induced structural alterations but rather assumes an inherent calcium-dependent cohesin-primed conformation.





    Categories: Journal Articles