scholarly journals Three-dimensional topology of the SMC2/SMC4 subcomplex from chicken condensin I revealed by cross-linking and molecular modelling

Open Biology ◽  
2015 ◽  
Vol 5 (2) ◽  
pp. 150005 ◽  
Author(s):  
Helena Barysz ◽  
Ji Hun Kim ◽  
Zhuo Angel Chen ◽  
Damien F. Hudson ◽  
Juri Rappsilber ◽  
...  
Keyword(s):  
Structure Prediction ◽  
Structural Information ◽  
Protein Complexes ◽  
Three Dimensional ◽  
Coiled Coil ◽  
Coiled Coils ◽  
Dimensional Structure ◽  
Cross Linking ◽  
Mitotic Chromosomes ◽  
Essential Components

SMC proteins are essential components of three protein complexes that are important for chromosome structure and function. The cohesin complex holds replicated sister chromatids together, whereas the condensin complex has an essential role in mitotic chromosome architecture. Both are involved in interphase genome organization. SMC-containing complexes are large (more than 650 kDa for condensin) and contain long anti-parallel coiled-coils. They are thus difficult subjects for conventional crystallographic and electron cryomicroscopic studies. Here, we have used amino acid-selective cross-linking and mass spectrometry combined with structure prediction to develop a full-length molecular draft three-dimensional structure of the SMC2/SMC4 dimeric backbone of chicken condensin. We assembled homology-based molecular models of the globular heads and hinges with the lengthy coiled-coils modelled in fragments, using numerous high-confidence cross-links and accounting for potential irregularities. Our experiments reveal that isolated condensin complexes can exist with their coiled-coil segments closely apposed to one another along their lengths and define the relative spatial alignment of the two anti-parallel coils. The centres of the coiled-coils can also approach one another closely in situ in mitotic chromosomes. In addition to revealing structural information, our cross-linking data suggest that both H2A and H4 may have roles in condensin interactions with chromatin.

scholarly journals Crystalline tubes of myosin subfragment-2 showing the coiled-coil and molecular interaction geometry.

1987 ◽  
Vol 105 (1) ◽  
pp. 403-415 ◽  
Author(s):  
R A Quinlan ◽  
M Stewart
Keyword(s):  
Thin Sheet ◽  
Three Dimensional ◽  
Coiled Coil ◽  
Precise Determination ◽  
Coiled Coils ◽  
Crystalline Lattice ◽  
Dimensional Structure ◽  
Chicken Breast ◽  
Myosin Subfragment

We have produced crystalline tubes of chicken breast myosin long subfragment-2 that show order to resolutions better than 2 nm. The tubes were formed from a thin sheet in which the myosin long subfragment-2 molecules were arranged on an approximately rectangular crystalline lattice with a = 14.1 +/- 0.2 nm and b = 3.9 +/- 0.1 nm in projection. Shadowing indicated that the tube wall was approximately 7 nm thick and that the sheets from which it was formed followed a right-handed helix. Superposition of the lattices from the top and bottom of the tube produced a moire pattern in negatively stained material, but images of single sheets were easily obtained by computer image processing. Although several molecules were superimposed perpendicular to the plane of the sheet, the modulation in density due to the coiled-coil envelope was clear, indicating that the coiled-coils in these molecules were in register (or staggered by an even number of quarter pitches). In projection the coiled-coil had an apparent pitch of 14.1 nm (the axial repeat of the unit cell), but the small number of molecules (probably four) superimposed perpendicular to the plane of the sheet meant that pitches within approximately 1 nm of this value could have shown a modulation. Therefore, a more precise determination of the coiled-coil pitch must await determination of the sheet's three-dimensional structure. The coiled-coils of adjacent molecules within the plane of the sheet were staggered by an odd number of quarter pitches. This arrangement was similar to that between paramyosin molecules in molluscan thick filaments and may have features in common with other coiled-coil protein assemblies, such as intermediate filaments. Each molecule in the crystal had two types of neighbor: one staggered by an odd number of quarter pitches and the other by an even number of quarter pitches, as has been proposed for the general packing of coiled-coils (Longley, W., 1975, J. Mol. Biol., 93:111-115). We propose a model for the detailed packing within the sheet whereby molecules are inclined slightly to the plane of the sheet so that its thickness is determined by the molecular length.

scholarly journals Complementing sequence-derived features with structural information extracted from fragment libraries for protein structure prediction

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Siyuan Liu ◽  
Tong Wang ◽  
Qijiang Xu ◽  
Bin Shao ◽  
Jian Yin ◽  
...  
Keyword(s):  
Protein Folding ◽  
Protein Structure ◽  
Protein Structure Prediction ◽  
Structure Prediction ◽  
Structural Information ◽  
Three Dimensional ◽  
Structural Features ◽  
Dimensional Structure ◽  
Fragment Assembly ◽  
Fragment Libraries

Abstract Background Fragment libraries play a key role in fragment-assembly based protein structure prediction, where protein fragments are assembled to form a complete three-dimensional structure. Rich and accurate structural information embedded in fragment libraries has not been systematically extracted and used beyond fragment assembly. Methods To better leverage the valuable structural information for protein structure prediction, we extracted seven types of structural information from fragment libraries. We broadened the usage of such structural information by transforming fragment libraries into protein-specific potentials for gradient-descent based protein folding and encoding fragment libraries as structural features for protein property prediction. Results Fragment libraires improved the accuracy of protein folding and outperformed state-of-the-art algorithms with respect to predicted properties, such as torsion angles and inter-residue distances. Conclusion Our work implies that the rich structural information extracted from fragment libraries can complement sequence-derived features to help protein structure prediction.

Automatedde novophasing and model building of coiled-coil proteins

2015 ◽  
Vol 71 (3) ◽  
pp. 606-614 ◽  
Author(s):  
Sebastian Rämisch ◽  
Robert Lizatović ◽  
Ingemar André
Keyword(s):  
Structure Prediction ◽  
Initial Phase ◽  
Model Building ◽  
De Novo ◽  
Protein Complexes ◽  
Coiled Coil ◽  
Coiled Coils ◽  
Phase Estimation ◽  
Molecular Replacement ◽  
Experimental Phasing

Models generated byde novostructure prediction can be very useful starting points for molecular replacement for systems where suitable structural homologues cannot be readily identified. Protein–protein complexes andde novo-designed proteins are examples of systems that can be challenging to phase. In this study, the potential ofde novomodels of protein complexes for use as starting points for molecular replacement is investigated. The approach is demonstrated using homomeric coiled-coil proteins, which are excellent model systems for oligomeric systems. Despite the stereotypical fold of coiled coils, initial phase estimation can be difficult and many structures have to be solved with experimental phasing. A method was developed for automatic structure determination of homomeric coiled coils from X-ray diffraction data. In a benchmark set of 24 coiled coils, ranging from dimers to pentamers with resolutions down to 2.5 Å, 22 systems were automatically solved, 11 of which had previously been solved by experimental phasing. The generated models contained 71–103% of the residues present in the deposited structures, had the correct sequence and had freeRvalues that deviated on average by 0.01 from those of the respective reference structures. The electron-density maps were of sufficient quality that only minor manual editing was necessary to produce final structures. The method, namedCCsolve, combines methods forde novostructure prediction, initial phase estimation and automated model building into one pipeline.CCsolveis robust against errors in the initial models and can readily be modified to make use of alternative crystallographic software. The results demonstrate the feasibility ofde novophasing of protein–protein complexes, an approach that could also be employed for other small systems beyond coiled coils.

scholarly journals RNA-Puzzles: A CASP-like evaluation of RNA three-dimensional structure prediction

RNA ◽  
2012 ◽  
Vol 18 (4) ◽  
pp. 610-625 ◽  
Author(s):  
J. A. Cruz ◽  
M.-F. Blanchet ◽  
M. Boniecki ◽  
J. M. Bujnicki ◽  
S.-J. Chen ◽  
...  
Keyword(s):  
Structure Prediction ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Three Dimensional Structure

scholarly journals Analysis of structural similarities between brain Thy-1 antigen and immunoglobulin domains. Evidence for an evolutionary relationship and a hypothesis for its functional significance

1981 ◽  
Vol 195 (1) ◽  
pp. 31-40 ◽  
Author(s):  
F E Cohen ◽  
J Novotný ◽  
M J E Sternberg ◽  
D G Campbell ◽  
A F Williams
Keyword(s):  
Functional Significance ◽  
Structure Prediction ◽  
Secondary Structure Prediction ◽  
Three Dimensional ◽  
Evolutionary Relationship ◽  
Dimensional Structure ◽  
Sequence Homologies ◽  
Beta Structure ◽  
Beta 2 Microglobulin

The Thy-1 membrane glycoprotein from rat brain is shown to have structural and sequence homologies with immunoglobulin (Ig) domains on the basis of the following evidence. 1. The two disulphide bonds of Thy-1 are both consistent with the Ig-fold. 2. The molecule contains extensive beta-structure as shown by the c.d. spectrum. 3. Secondary structure prediction locates beta-strands along the sequence in a manner consistent with the Ig-fold. 4. On the basis of rules derived from known beta-sheet structures, a three-dimensional structure with the Ig-fold is predicted as favourable for Thy-1. 5. Sequences in the proposed beta-strands of Thy-1 and known beta-strands of Ig domains show significant sequence homology. This homology is statistically more significant than for the comparison of proposed beta-strand sequences of beta 2-microglobulin with Ig domains. An hypothesis is presented for the possible functional significance of an evolutionary relationship between Thy-1 and Ig. It is suggested that both Thy-1 and Ig evolved from primitive molecules, with an Ig fold, which mediated cell--cell interactions. The present-day role of Thy-1 may be similar to that of the primitive domain.

Televisualization: An Aid To Collaborative Research In Molecular Structure Biology

1998 ◽  
Vol 4 (S2) ◽  
pp. 32-33
Author(s):  
M. F. Schmid ◽  
P. Matsudaira ◽  
M. T. Dougherty ◽  
M. B. Sherman ◽  
C. Henn ◽  
...  
Keyword(s):  
Image Processing ◽  
Actin Filaments ◽  
Collaborative Research ◽  
Horseshoe Crab ◽  
Hexagonal Lattice ◽  
Three Dimensional ◽  
Limulus Polyphemus ◽  
Dimensional Structure ◽  
Cross Linking ◽  
Tilt Series

Collaboration between local microscopists and image processing specialists, and their remote biological colleagues, has been hampered by the difficulty of i) transferring the three-dimensional reconstructions of macromolecules resulting from the cryomicroscopy and image processing, ii) viewing the results in a meaningful way, and iii) communicating the results and the interpretations derived therefrom to each other.The acrosomal process is an intracellular quasi-crystalline organelle in the head of the sperm of the horseshoe crab Limulus polyphemus. It consists of 100 - 130 actin-scruin filaments packed together in a pseudo-hexagonal lattice and is up to 60 μm long with a diameter of 0.1 μm. Scruin-scruin interactions are responsible for cross-linking the actin filaments together in the bundle. Our goal was to reveal interfilament interactions in the bundle. We have taken tilt series images in the electron microscope to reconstruct its three-dimensional structure at 45 Å resolution.

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