scholarly journals Cryo-ET analysis of budding yeast synaptonemal complexes in situ

2019 ◽  
Author(s):  
Olivia X. Ma ◽  
Shujun Cai ◽  
Jian Shi ◽  
Lu Gan
Keyword(s):  
Triple Helix ◽  
Phase Contrast ◽  
Central Element ◽  
Super Resolution ◽  
Native Structure ◽  
Homologous Chromosomes ◽  
Triple Helices ◽  
Subtomogram Averaging ◽  
Electron Cryotomography

ABSTRACTThe synaptonemal complex (SC) is the large, conserved, proteinaceous scaffold that assembles between and holds together homologous chromosomes in meiotic prophase. Knowledge of the native structure of this complex is needed to evaluate how the SC carries out its functions. Traditional electron microscopy and super-resolution light microscopy have revealed that in many organisms, the SC has a ladder-like structure: two rail-like lateral elements are bridged by a set of rung-like transverse filaments. The transverse filaments are connected along their centers by a central element. To determine the 3-D architecture of the SC in situ, we studied frozen-hydrated meiotic yeast cell cryosections by Volta phase-contrast electron cryotomography and subtomogram analysis. We find the SC is built from triple-helical filaments that pack into dense polycrystalline bundles. These structures are also abundant in the polycomplexes of pachytene-arrested cells. Dissolution by 1,6-hexanediol treatment suggests that these triple-helical filaments belong to the central region of the SCs. Subtomogram averaging revealed that the SC’s triple-helical filaments are up to 12-nm thick and have a 5-nm rise and 130-nm pitch. Single triple-helices and polymers thinner than the triple helix, such as single or double strands, were not detected, consistent with the strong self-oligomerization properties of SC proteins. The dense packing of SC subunits supports the notion that the SC’s mechanical properties help coordinate the rapid end-to-end communication across synapsed chromosomes.

scholarly journals A close-to-native structure of the synaptonemal complex

2021 ◽  
Author(s):  
Rosario Ortiz ◽  
Olga M Echeverria ◽  
Sergej Masich ◽  
Christer Hoog ◽  
Abrahan Hernandez-Hernandez
Keyword(s):  
Electron Microscopy ◽  
Genetic Variability ◽  
Synaptonemal Complex ◽  
Central Region ◽  
Genetic Material ◽  
Central Element ◽  
Structural Models ◽  
Super Resolution ◽  
Native Structure ◽  
Homologous Chromosomes

Genetic variability in sexually reproducing organisms results from an exchange of genetic material between homologous chromosomes. The genetic exchange mechanism is dependent on the synaptonemal complex (SC), a protein structure localized between the homologous chromosomes. Current structural models of the SC are based on electron microscopy, super resolution, and expansion microscopy studies using chemical fixatives and sample dehydration of gonads, which are methodologies known to produce structural artifacts. We have developed a novel electron microscopy sample-preparation approach where pachytene cells are isolated from mouse testis by FACS, followed by cryo-fixation and cryo-substitution to achieve visualization of a close-to-native structure of the SC. We found that the central region of the SC was wider than previously recognized, and the transverse filaments more densely packed in the central region. Furthermore, we identified a structure nucleating the central element of the SC.

scholarly journals In situ structure and organization of the influenza C virus surface glycoprotein

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Steinar Halldorsson ◽  
Kasim Sader ◽  
Jack Turner ◽  
Lesley J. Calder ◽  
Peter B. Rosenthal
Keyword(s):  
Membrane Fusion ◽  
Hexagonal Lattice ◽  
Surface Glycoprotein ◽  
Structural Basis ◽  
Virus Surface ◽  
The Matrix ◽  
Influenza C Virus ◽  
Subtomogram Averaging ◽  
Electron Cryotomography

AbstractThe lipid-enveloped influenza C virus contains a single surface glycoprotein, the haemagglutinin-esterase-fusion (HEF) protein, that mediates receptor binding, receptor destruction, and membrane fusion at the low pH of the endosome. Here we apply electron cryotomography and subtomogram averaging to describe the structural basis for hexagonal lattice formation by HEF on the viral surface. The conformation of the glycoprotein in situ is distinct from the structure of the isolated trimeric ectodomain, showing that a splaying of the membrane distal domains is required to mediate contacts that form the lattice. The splaying of these domains is also coupled to changes in the structure of the stem region which is involved in membrane fusion, thereby linking HEF’s membrane fusion conformation with its assembly on the virus surface. The glycoprotein lattice can form independent of other virion components but we show a major role for the matrix layer in particle formation.

scholarly journals Underhydroxylated minor cartilage collagen precursors cannot form stable triple helices

1988 ◽  
Vol 250 (1) ◽  
pp. 65-70 ◽  
Author(s):  
C C Clark ◽  
C F Richards
Keyword(s):  
Chick Embryo ◽  
Triple Helix ◽  
Iron Chelator ◽  
Prolyl Hydroxylase ◽  
Type Ii ◽  
Native Structure ◽  
Lysyl Hydroxylase ◽  
Free Cells ◽  
Triple Helices ◽  
Matrix Free

Matrix-free cells from chick-embryo sterna were incubated with various concentrations of 2,2′-bipyridyl, an iron chelator that inhibits prolyl hydroxylase and lysyl hydroxylase. At concentrations in the region of 0.1 mM, significant effects on cartilage collagen hydroxylation and secretion were observed. When the underhydroxylated collagens were subsequently digested with chymotrypsin or chymotrypsin plus trypsin at 4 degrees C for 15 min, the minor cartilage collagen precursors (namely types IX and XI) were extensively degraded; type II procollagen was only partially susceptible and was converted into underhydroxylated collagen. The results demonstrate that there were significant differences in triple-helix stability among cartilage collagens such that the underhydroxylated minor collagen precursors were unable to attain a native structure under conditions where type II procollagen was successful.

scholarly journals Helical arrays of U-shaped ATP synthase dimers form tubular cristae in ciliate mitochondria

2016 ◽  
Vol 113 (30) ◽  
pp. 8442-8447 ◽  
Author(s):  
Alexander W. Mühleip ◽  
Friederike Joos ◽  
Christoph Wigge ◽  
Achilleas S. Frangakis ◽  
Werner Kühlbrandt ◽  
...  
Keyword(s):  
Atp Synthase ◽  
Protein Complexes ◽  
Paramecium Tetraurelia ◽  
Mitochondrial Atp Synthase ◽  
Structural Differences ◽  
Membrane Protein Complexes ◽  
Subtomogram Averaging ◽  
Electron Cryotomography ◽  
Energy Converting

F1Fo-ATP synthases are universal energy-converting membrane protein complexes that synthesize ATP from ADP and inorganic phosphate. In mitochondria of yeast and mammals, the ATP synthase forms V-shaped dimers, which assemble into rows along the highly curved ridges of lamellar cristae. Using electron cryotomography and subtomogram averaging, we have determined the in situ structure and organization of the mitochondrial ATP synthase dimer of the ciliate Paramecium tetraurelia. The ATP synthase forms U-shaped dimers with parallel monomers. Each complex has a prominent intracrista domain, which links the c-ring of one monomer to the peripheral stalk of the other. Close interaction of intracrista domains in adjacent dimers results in the formation of helical ATP synthase dimer arrays, which differ from the loose dimer rows in all other organisms observed so far. The parameters of the helical arrays match those of the cristae tubes, suggesting the unique features of the P. tetraurelia ATP synthase are directly responsible for generating the helical tubular cristae. We conclude that despite major structural differences between ATP synthase dimers of ciliates and other eukaryotes, the formation of ATP synthase dimer rows is a universal feature of mitochondria and a fundamental determinant of cristae morphology.

scholarly journals Lateral Elements Inside Synaptonemal Complex-Like Polycomplexes in ndt80 Mutants of Yeast Bind DNA

Genetics ◽  
2003 ◽  
Vol 163 (2) ◽  
pp. 539-544 ◽  
Author(s):  
Hasanuzzaman Bhuiyan ◽  
Gunilla Dahlfors ◽  
Karin Schmekel
Keyword(s):  
In Situ Hybridization ◽  
Electron Microscope ◽  
Synaptonemal Complex ◽  
Immunoelectron Microscopy ◽  
Meiotic Prophase ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Meiotic Prophase I ◽  
Dna Antibodies

Abstract The synaptonemal complex (SC) keeps the synapsed homologous chromosomes together during pachytene in meiotic prophase I. Structures that resemble stacks of SCs, polycomplexes, are sometimes found before or after pachytene. We have investigated ndt80 mutants of yeast, which arrest in pachytene. SCs appear normal in spread chromosome preparations, but are only occasionally found in intact nuclei examined in the electron microscope. Instead, large polycomplexes occur in almost every ndt80 mutant nucleus. Immunoelectron microscopy using DNA antibodies show strong preferential labeling to the lateral element parts of the polycomplexes. In situ hybridization using chromosome-specific probes confirms that the chromosomes in ndt80 mutants are paired and attached to the SCs. Our results suggest that polycomplexes can be involved in binding of chromosomes and possibly also in synapsis.

scholarly journals Visualizing the Molecular Machines of Bacterial Motility In-situ with Electron Cryotomography

2006 ◽  
Vol 12 (S02) ◽  
pp. 398-399
Author(s):  
GJ Jensen ◽  
GE Murphy ◽  
GP Henderson ◽  
Z Li ◽  
A Komeili ◽  
...  
Keyword(s):  
Molecular Machines ◽  
Bacterial Motility ◽  
Electron Cryotomography

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005

scholarly journals Interindividual size heteromorphism of NOR and chromosomal location of 5S rRNA genes in Iheringichthys labrosus

2007 ◽  
Vol 50 (1) ◽  
pp. 141-146 ◽  
Author(s):  
Rafael Augusto de Carvalho ◽  
Ana Lúcia Dias
Keyword(s):  
Chromosomal Location ◽  
5S Rdna ◽  
Rrna Genes ◽  
Telomeric Region ◽  
Fluorescent Staining ◽  
Homologous Chromosomes ◽  
Rdna Probe ◽  
5S Rrna Genes ◽  
Iheringichthys Labrosus

Twenty-five specimens of Iheringichthys labrosus from the Capivara Reservoir were analysed cytogenetically. AgNORs were detected in a pair of ST chromosomes, in the telomeric region of the long arm. Some individuals showed size heteromorphism of this region between homologous chromosomes. Treatment with CMA3 displayed GC-rich regions corresponding to the AgNOR pair, plus other fluorescent staining. In situ hybridization by fluorescence (FISH) with the 18S rDNA probe showed only one pair of stained chromosomes, confirming the heteromorphism observed with AgNO3 and CMA3 in some individuals. The 5S rDNA probe revealed telomeric staining on the long arm of a pair of chromosomes of the ST-A group, probably different from the NOR pair.

scholarly journals Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta

1983 ◽  
Vol 211 (2) ◽  
pp. 295-302 ◽  
Author(s):  
E Odermatt ◽  
J Risteli ◽  
V van Delden ◽  
R Timpl
Keyword(s):  
Human Placenta ◽  
Triple Helix ◽  
Structural Diversity ◽  
Helical Conformation ◽  
Basic Unit ◽  
Bacterial Collagenase ◽  
Disulphide Bonds ◽  
Triple Helices ◽  
Electron Microscopical ◽  
Polypeptide Chains

Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion. Reduction of as little as 5% of the disulphide bonds produces mainly monomeric triple helices (Mr about 160 000) with Tm 32 degrees C. Partially reduced material can be separated into triple-helical and non-collagenous domains by proteolysis. Pepsin releases a collagenous component with chains of Mr 38 000. Bacterial collagenase liberates two non-collagenous segments (Mr 15 000-30 000) rich in cystine. Treatment with collagenase before reduction separates intima collagen into a large fragment composed of collagenous (Tm 41 degrees C) and non-collagenous structures and a single non-collagenous segment. The data support the electron-microscopical model of intima collagen [Furthmayr, Wiedemann, Timpl, Odermatt & Engel (1983) Biochem. J. 211, 303-311], indicating that the basic unit of the fragment consists of a continuous triple helix joining two globular domains.

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