Different Mechanisms of Resistance toBacillus thuringiensis Toxins in the Indianmeal Moth

ABSTRACT Susceptibility to protoxin and toxin forms of Cry1Ab and the binding of 125I-labeled Cry1Ab and Cry1Ac has been examined in three Plodia interpunctella colonies, one susceptible (688s) and two resistant (198r and Dplr) to Bacillus thuringiensis. Toxicological studies showed that the 198r colony was 11-fold more resistant to Cry1Ab protoxin than to Cry1Ab activated toxin, whereas the Dplr colony was 4-fold more resistant to protoxin versus toxin. Binding results with 125I-labeled toxins indicated the occurrence of two different binding sites for Cry1Ab in the susceptible insects, one of them shared with Cry1Ac. Cry1Ab binding was found to be altered in insects from both resistant colonies, though in different ways. Compared with the susceptible colony, insects from the Dplr colony showed a drastic reduction in binding affinity (60-fold higher Kd ), although they had similar concentrations of binding sites. Insects from the 198r colony showed a slight reduction in both binding affinity and binding site concentration (five-fold-higherKd and ca. three-fold-lowerRt compared with the 688s colony). No major difference in Cry1Ac binding was found among the three colonies. The fact that the 198r colony also has a protease-mediated mechanism of resistance (B. Oppert, R. Hammel, J. E. Throne, and K. J. Kramer, J. Biol. Chem. 272:23473–23476, 1997) is in agreement with our toxicological data in which this colony has a different susceptibility to the protoxin and toxin forms of Cry1Ab. It is noteworthy that the three colonies used in this work derived originally from ca. 100 insects, which reflects the high variability and high frequency of B. thuringiensisresistance genes occurring in natural populations.

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Enhanced testosterone secretion in adult rams after establishment of a high-frequency, low-amplitude pattern of LH pulses in the nonbreeding season occurs without changes in the number or binding affinity of testicular LH receptors

Acta Endocrinologica ◽

10.1530/acta.0.1220055 ◽

1990 ◽

Vol 122 (1) ◽

pp. 55-61 ◽

Cited By ~ 2

Author(s):

Lee M. Sanford ◽

Susan J. Baker

Keyword(s):

Binding Affinity ◽

Binding Sites ◽

High Frequency ◽

Leydig Cells ◽

Jugular Vein ◽

Pulse Amplitude ◽

Nonbreeding Season ◽

Testosterone Secretion ◽

Low Amplitude ◽

Amplitude Pattern

Abstract When the LH signal in the ram is changed from one of large and infrequent pulses to one of small and frequent pulses, the testes quickly become more responsive to LH and testosterone secretion is elevated, perhaps because the number and (or) binding affinity of testicular LH receptors have increased. An experiment was undertaken in the nonbreeding season (July) with 10 adult Dorset × Leicester × Suffolk rams that were about 3.5 years of age and 69 ± 2 kg in body weight. Rams were given injections into the jugular vein of either 5 μg NIH-LH-S24 (in 1 ml saline) or vehicle every 80 min for 6 days. LH treament produced a series of LH pulses that occurred three times more frequently and were 70% less in amplitude than pulses in the control rams, without causing mean LH concentration to increase. Endogenously produced LH pulses were not evident in the treated rams after LH injection began. The modified LH-pulse pattern elevated mean testosterone concentration by 150% (assessed on days 2 and 5), and caused the cumulative testosterone response to LH pulses, estimated by multiplying testosterone-pulse amplitude by frequency per 6 h, to increase progressively by 180% (days −2 through 5). Enhanced testicular steroidogenic activity, presumably due to greater enzymatic activity and cholesterol availability within Leydig cells, was not associated with increases in either the concentration or affinity of LH-binding sites in the testis (assessed on days 3 and 6).

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The correlation between Na+ channel subunits and scorpion toxin-binding sites. A study in rat brain synaptosomes and in brain neurons developing in vitro.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)57338-0 ◽

1988 ◽

Vol 263 (3) ◽

pp. 1542-1548

Author(s):

E Jover ◽

A Massacrier ◽

P Cau ◽

M F Martin ◽

F Couraud

Keyword(s):

Rat Brain ◽

Binding Sites ◽

Scorpion Toxin ◽

Na Channel ◽

Brain Neurons ◽

Rat Brain Synaptosomes ◽

Toxin Binding ◽

Brain Synaptosomes

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Low-affinity transcription factor binding sites shape morphogen responses and enhancer evolution

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2013.0018 ◽

2013 ◽

Vol 368 (1632) ◽

pp. 20130018 ◽

Cited By ~ 67

Author(s):

Andrea I. Ramos ◽

Scott Barolo

Keyword(s):

Transcription Factor ◽

Binding Affinity ◽

Binding Sites ◽

Target Genes ◽

Gene Activation ◽

Transcriptional Response ◽

Morphogen Gradients ◽

Weak Binding ◽

Initial Hypothesis

In the era of functional genomics, the role of transcription factor (TF)–DNA binding affinity is of increasing interest: for example, it has recently been proposed that low-affinity genomic binding events, though frequent, are functionally irrelevant. Here, we investigate the role of binding site affinity in the transcriptional interpretation of Hedgehog (Hh) morphogen gradients . We noted that enhancers of several Hh-responsive Drosophila genes have low predicted affinity for Ci, the Gli family TF that transduces Hh signalling in the fly. Contrary to our initial hypothesis, improving the affinity of Ci/Gli sites in enhancers of dpp , wingless and stripe , by transplanting optimal sites from the patched gene, did not result in ectopic responses to Hh signalling. Instead, we found that these enhancers require low-affinity binding sites for normal activation in regions of relatively low signalling. When Ci/Gli sites in these enhancers were altered to improve their binding affinity, we observed patterning defects in the transcriptional response that are consistent with a switch from Ci-mediated activation to Ci-mediated repression. Synthetic transgenic reporters containing isolated Ci/Gli sites confirmed this finding in imaginal discs. We propose that the requirement for gene activation by Ci in the regions of low-to-moderate Hh signalling results in evolutionary pressure favouring weak binding sites in enhancers of certain Hh target genes.

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Association of Engrailed homeoproteins with vesicles presenting caveolae-like properties

Development ◽

10.1242/dev.124.10.1865 ◽

1997 ◽

Vol 124 (10) ◽

pp. 1865-1875 ◽

Cited By ~ 4

Author(s):

A. Joliot ◽

A. Trembleau ◽

G. Raposo ◽

S. Calvet ◽

M. Volovitch ◽

...

Keyword(s):

Binding Sites ◽

Cell Adhesion Molecule ◽

Proteolytic Enzymes ◽

Subcellular Fractionation ◽

Low Density ◽

Toxin Binding ◽

Neural Cell Adhesion ◽

Neural Tissues ◽

Triton X ◽

Specific Membrane

We report here that the homeoproteins Engrailed-1 and Engrailed-2 are present in specific non-nuclear subcellular compartments. Using electron microscopy, we observed that chick-Engrailed-2 expressed in COS-7 cells associates with membrane fractions that are characterized as caveolae. This characterization is based on morphological, biochemical and immunological criteria such as, in particular, the absence of clathrin coat and the presence of caveolin and cholera toxin-binding sites. These data are fully confirmed by subcellular fractionation experiments, which demonstrate that transfected chick-Engrailed-2 is present in low density membrane fractions that are resistant to Triton X-100, enriched in caveolin and solubilized by the addition of a cholesterol-binding detergent, a set of properties highly characteristic of caveolae. The association of Engrailed-2 with specific membrane fractions observed after transfection in COS-7 cells is also observed for endogenous Engrailed-1 and Engrailed-2 expressed at late embryonic stages in the cerebellum and posterior mesencephalon of the rodent. Indeed, the two proteins are present in membrane fractions that bear all the characteristics of microdomains or caveolae-like domains, i.e. Triton X-100 resistance, saponin solubilization, low density on sucrose gradients, enrichment in glycosphingolipid GM1, absence of transmembrane Neural Cell Adhesion Molecule, presence of the glypiated (GPI-anchored) glycoprotein F3/F11 and of the acylated growth-associated protein GAP-43. Finally we demonstrate that part of the membrane-associated Engrailed, either expressed in COS-7 cells or endogenously present in neural tissues, is not accessible to proteolytic enzymes unless the membranes have been permeabilized with detergent. This study suggests that, in addition to their well-known presence in the nucleus, Engrailed proteins are also associated with caveolae-like vesicles that are primarily transported anterogradely into the axon, and that they can get access to a compartment compatible with secretion.

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Acetylcholine Receptors of Cultured Muscle Cells Demonstrated with Ferritin-α-Bungarotoxin Conjugates

Journal of Cell Science ◽

10.1242/jcs.16.2.473 ◽

1974 ◽

Vol 16 (2) ◽

pp. 473-479

Author(s):

B. T. HOURANI ◽

B. F. TORAIN ◽

M. P. HENKART ◽

R. L. CARTER ◽

V. T. MARCHESI ◽

...

Keyword(s):

Binding Sites ◽

Acetylcholine Receptors ◽

Surface Membrane ◽

Freeze Fracture ◽

Muscle Cells ◽

Muscle Fibres ◽

Toxin Binding ◽

Thin Section Electron Microscopy ◽

Section Electron ◽

Small Clusters

α-Bungarotoxin-ferritin conjugates were used to visualize by freeze-fracture and thin-section electron microscopy toxin-binding sites, presumably acetylcholine (ACh) receptors, in membranes of muscle cells grown in tissue culture. Toxin conjugated to ferritin by a glutaraldehyde reaction and purified by column chromatography in a buffer of high ionic strength remains active in blocking the effect of iontophoretically applied ACh. The potency of the conjugates was decreased 5-10 times compared to native α-bungarotoxin. Toxin-ferritin conjugates were identified in small clusters which were not uniformly distributed over the surface membrane. Binding was inhibited by preincubation in D-tubocurare or unconjugated toxin. The relation of the clusters to the non-uniform distribution of ACh sensitivity and α-bungarotoxin binding on cultured muscle fibres is discussed.

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Supramolecular self-assemblies of inverted cucurbit[7]uril with biogenic amines

New Journal of Chemistry ◽

10.1039/c8nj04697b ◽

2019 ◽

Vol 43 (1) ◽

pp. 407-412

Author(s):

Pei-Hui Shan ◽

Zhi-Rui Zhang ◽

Dong Bai ◽

Bing Bian ◽

Zhu Tao ◽

...

Keyword(s):

Biogenic Amines ◽

Binding Affinity ◽

Biogenic Amine ◽

Binding Sites ◽

Experimental Results ◽

Binding Interactions ◽

Strong Binding

The binding interactions between six biogenic amine guests and the iQ[7] host were investigated. The experimental results have revealed that iQ[7] shows strong binding affinity towards five of the studied biogenic amines, but not histamine, and that the binding sites are different depending on the structure of the biogenic amine.

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Cytogenetic differentiation between Palearctic and Nearctic populations of Chironomus plumosus L. (Diptera, Chironomidae)

Genome ◽

10.1139/g99-014 ◽

1999 ◽

Vol 42 (5) ◽

pp. 797-815 ◽

Cited By ~ 24

Author(s):

Malcolm G Butler ◽

Iya I Kiknadze ◽

Veronica V Golygina ◽

Jon Martin ◽

Albina G Istomina ◽

...

Keyword(s):

Atlantic Ocean ◽

High Frequency ◽

Natural Populations ◽

Inversion Polymorphism ◽

Chironomus Plumosus ◽

Chromosomal Banding ◽

Great Divergence ◽

Holarctic Species

Macrogeographic patterns of polytene chromosomal banding sequences were studied in natural populations of the Holarctic species Chironomus plumosus. Of the 31 inversion sequences now known, 16 are endemic to the Palearctic, 7 are endemic to the Nearctic, and 8 are Holarctic sequences common to both zoogeographic zones. Differences in the sets of inversion sequences found on each continent, plus differing frequencies of Holarctic sequences, result in great overall divergence of karyotypes on the two continents. The karyotype of Nearctic C. plumosus differs from that of Palearctic populations primarily by the presence of a homozygous Nearctic sequence in arm A (n'plu A9), along with fixation (h'plu C2, h'plu E2, and h'plu F1), or high frequency (h'plu D2), of Holarctic sequences which are present but less frequent in the Palearctic. Although long continental isolation has led to great divergence of karyotypes on opposite sides of the Atlantic Ocean, all populations of C. plumosus show sufficient cytogenetic similarity to constitute a single Holarctic species.Key words: karyotype, inversion polymorphism, cytogenetic distances, Chironomus.

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Scatchard Plot and Heterogeneity in Binding Affinity of Labeled and Unlabeled Ligand

Clinical Chemistry ◽

10.1093/clinchem/21.12.1769 ◽

1975 ◽

Vol 21 (12) ◽

pp. 1769-1773 ◽

Cited By ~ 23

Author(s):

H J G Hollemans ◽

R M Bertina

Keyword(s):

Binding Affinity ◽

Binding Sites ◽

Mathematical Expression ◽

Molar Concentration ◽

Scatchard Plot ◽

Affinity Constant

Abstract In saturation analysis the Scatchard plot is a generally accepted method for calculation of the affinity constant, K, and the molar concentration, q, of the binder. However, in a system where the K's for the labeled and unlabeled ligand are unequal, a nonlinear plot can be obtained from which incorrect values for K and q may be calculated. This paper mathematically explains how the plot may deviate and under which conditions there will be a maximum in the curve. When the binding sites are homogeneous, the coordinates of this maximum can be used to calculate K and q. A general mathematical expression is derived on the basis of which a linear curve can be constructed for calculation of q and K, which is valid even when affinity for the labeled and unlabeled ligand is not identical.

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EFFECT OF ENDOCRINE MANIPULATIONS ON GLUCOCORTICOID BINDING CAPACITY IN RAT SKELETAL MUSCLE

Acta Endocrinologica ◽

10.1530/acta.0.0880199 ◽

1978 ◽

Vol 88 (1) ◽

pp. 199-208 ◽

Cited By ~ 15

Author(s):

Michael Mayer ◽

Fred Rosen

Keyword(s):

Skeletal Muscle ◽

Binding Sites ◽

Binding Capacity ◽

Specific Binding ◽

Female Rats ◽

Receptor Protein ◽

Slight Reduction ◽

Binding Assays ◽

Receptor Concentration ◽

Streptozotocin Induced Diabetes

ABSTRACT [3H]Dexamethasone binding capacity in rat muscle cytosol was determined after various endocrine manipulations in an attempt to identify factors which might regulate the level of the cytoplasmic hormone receptor protein. Hypophysectomy and adrenalectomy markedly increased the specific binding of [3H]dexamethasone in skeletal muscle cytosol, while implantation of the MtT tumour which secretes ACTH and growth hormone, as well as treatment with glucocorticoids reduced the glucocorticoid specific binding. Since the effects of hypophysectomy and the MtT tumour depend on the presence of the adrenals, they appear to be mediated via changes in circulating glucocorticoid level. Alloxan- or streptozotocin-induced diabetes caused only a slight reduction in the binding of [3H]dexamethasone in muscle, suggesting that the enhanced responsiveness to glucocorticoids in diabetes is not due to increased glucocorticoid receptor activity. There is a sex-dependent effect on binding, female rats having a higher concentration of binding sites. Furthermore, treatment with the synthetic androgen fluoxymesterone or with glucocorticoids reduces binding, while oestradiol-17β enhances it. The changes in glucocorticoid binding capacity induced by the various endocrine manipulations appear to reflect mainly changes in receptor concentration rather than occupancy, since the binding assays were preformed after a suitable time allowance for removal of the administered hormones by metabolism.

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