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Query: UNIPROT:P06889 (Mol)
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The nuclear thyroid hormone receptors isolated from cultured human hepatoma cells (Hep G2) were characterized and compared with those from cultured human fibroblasts and rat liver. The Hep G2 nuclear thyroid hormone receptors had an affinity constant (Ka) of 2.1 X 10(10) M-1 and maximal binding capacity (MBC) of 21.0 fmol/100 micrograms DNA for T3 in assays performed on isolated nuclei. 16% of nuclear receptors were released into the media during incubation and had the same Ka. Salt-extracted receptors had a Ka of 1.8 X 10(10) M-1 and MBC of 0.1 pmol/mg protein for T3. Density gradient sedimentation and gel filtration chromatography revealed a sedimentation coefficient of 3.4 S and Stokes radius of 34 A. From these values, a molecular weight of 49,000 and total frictional ratio (f/f0) of 1.4 were calculated, suggesting an asymmetrical shape of the receptor molecule. Heat inactivation occurred with t1/2 of 28.1, 18.0, and 7.9 min at 38, 43, 45 degrees C, respectively. Isoelectric focusing (IEF) of Hep G2 nuclear receptors demonstrated T3 binding proteins at pH 5.3-5.5, 5.7, and 5.9. Evidence that these are nuclear thyroid hormone receptors includes the following: Triiodothyroacetic acid was the most potent competitor of [125I]T3 binding to these proteins followed by L-T3, and L-T4. Cytosolic protein, human serum, and fetal calf serum failed to show the same T3 binding proteins. Ka of these proteins measured by T3 displacement was 1.1-3.2 X 10(9) M-1. Human fibroblast nuclear extract showed similar T3 binding pattern in IEF, except for a slight difference in pI of an acidic band.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1987 May
PMID:Thyroid hormone receptors in a human hepatoma cell line: multiple receptor forms on isoelectric focusing. 303 21

Salt and acid solubility of collagen are thought to reflect its degree of crosslinking. In order to examine postoperative changes in crosslinking of intestinal collagen, which are of importance to the stability of the intestinal wall, we have investigated the solubility of hydroxyproline in rabbit ileum and colon, both in unwounded intestine and after construction of an anastomosis. Solubility in salt and dilute acid was increased by a sonication procedure. This way, 9% of total hydroxyproline in the unwounded colonic wall was salt soluble and 65% acid soluble. A similar distribution was observed in ileum. Three days after operation the salt-soluble fraction was significantly elevated in samples from the anastomotic area. In colon, this increase also persisted 7 days postoperatively. Comparison of anastomotic samples collected 3 and 7 days after surgery shows a significant decrease in the acid-soluble and a significant increase in the solid fraction. This phenomenon occurs both in ileum and colon. These results indicate that during the first days after operation the integrity of the intestinal wall is weakened not only by a loss of collagen, but also by a changed solubility of the remaining collagen.
Exp Mol Pathol 1985 Oct
PMID:Solubility of tissue hydroxyproline in experimental intestinal anastomoses. 404 44

The concentration of thyroid hormone nuclear receptors varies from one tissue to another, the anterior pituitary (AP) gland possessing the highest. Since 3,5,3',1-triiodothyronine (T3) controls within a narrow range the secretion of TSH from the pituitary gland, this study was carried out to establish whether T3 modulates its own pituitary nuclear receptors and if so, whether this modulation is correlated with the thyroidal status and TSH secretion. Salt-solubilized T3 nuclear receptors were measured in the AP gland of thyroidectomized and intact adult male rats as well as in thyroidectomized rats treated with T3. In intact male rats the maximum binding capacity of pituitary T3 nuclear receptors (MBC-T3nR), determined by Scatchard analysis, was 578 +/- 45 fmoles T3/mg protein or 27 +/- 3 fmoles T3/AP (mean +/- SEM, n = 19). 2 weeks after thyroidectomy there was a marked decrease in serum T3 and T4 concentrations as well as in the MBC-T3nR (231 +/- 26 fmoles T3/mg protein or 9.3 +/- 1.2 fmoles T3/AP, n = 7) which was still observed 8 and 16 weeks after thyroidectomy. The affinity constant (Ka) of T3 for its pituitary nuclear receptors was significantly greater in thyroidectomized rats than in intact rats (3.61 +/- 0.70 vs. 1.09 +/- 0.15 X 10(10) M-1, P less than 0.001). To test whether treatment with T3 would restore a normal MBC-T3nR, 2-week thyroidectomized rats were injected with T3(0.5 micrograms/100 g b.w.) and killed 10 min, 1, 3, 15 or 24 h after T3 injection. 10 min after T3 injection MBC-T3nR was not altered but it returned to normal values 1 h after injection (441 +/- 97 fmoles T3/mg protein) and was maintained so for at least 3 h. 15 h after T3 injection MBC-T3nR was again decreased in spite of serum T3 levels that were twice as high as in normal rats. In contrast, when T3 was injected at the dose of 1.0 micrograms/100 g b.w. the MBC-T3nR was maintained within the normal range as long as 24 h after the injection (428 +/- 125 fmoles T3/mg protein) with serum T3 concentrations that were twice the normal levels (1.27 +/- 0.06 vs. 0.67 +/- 0.01 ng/ml). These results support the hypothesis that T3 modulates the concentration of its own nuclear receptors in the rat pituitary gland. The absence of any effect of T3 10 min after injection is suggestive of an effect of T3 on the synthesis of its receptors rather than on an alteration of unoccupied receptors that would require T3 for adequate configuration and detection. This modulation of pituitary T3 receptors by T3 may provide an additional mechanism of regulation of TSH secretion in thyroid insufficiency.
Mol Cell Endocrinol 1983 Dec
PMID:Modulation of thyroid hormone nuclear receptor levels by L-triiodothyronine (T3) in the rat pituitary. 631 85

CD spectra of poly(dA-dT).poly(dA-dT) in low salt (10-100 mM NaCl) and high salt (4-6 M CsF) are different i.e. 275 nm band gets inverted in going from low to high salt (Vorhickova et. al., J. Mol. Biol. 166, 85, 1983). However, from CD spectra alone it is not possible to decipher any structural differences that might exist between the low and high salt forms of poly(dA-dT).poly(dA-dT). Hence, we took recourse to high resolution NMR spectroscopy to understand the structural properties of poly(dA-dT).poly(dA-dT) in low and high salt. A detailed analysis of shielding constants and extensive use of NOE studies under minimum spin diffusion conditions using C(8)-deuterated poly(dA-dT).poly(dA-dT) enabled us to come up with the following conclusions (i) base-pairing is Watson-Crick under low and high salt conditions. (ii) under both the conditions of salt the experimental data can be explained in terms of an equilibrium blend of right and left-handed B-DNA duplexes with the left-handed form 70% and the right-handed 30%. In a 400 base pairs long poly(dA-dT).poly(dA-dT) (as used in this study), equilibrium between right and left-handed helices can also mean the existence of both helical domains in the same molecule with fast interchange between these domains or/and unhindered motion/propagation of these domains along the helix axis. (iii) However, there are other structural differences between the low and high salt forms of poly(dA-dT).poly(dA-dT); under the low salt condition, right- and left-handed B-DNA duplexes have mononucleotide as a structural repeat while under the high salt conditions, right- and left-handed B-DNA duplexes have dinucleotide as a structural repeat. In the text we provide the listing of torsion angles for the low and high salt structural forms. (iv) Salt (CsF) induced structural transition in poly(dA-dT).poly(dA-dT) occurs without any breakage of Watson-Crick pairing. (v) The high salt form of poly(dA-dT).poly(dA-dT) is not the left-handed Z-helix. Although the results above from NMR data are quite unambiguous, a question still remains i.e. what does the salt (CsF) induced change in the CD spectra of poly(dA-dT).poly(dA-dT) really indicate? Interestingly, we could show that the salt (CsF) induced change in poly(dA-dT).poly(dA-dT) is quite similar to that caused by a basic polypeptide viz. poly-L(Lys2-Ala)n i.e. both the agents induced a psi-structure in DNA.
 ...
PMID:Solution structure of poly(dA-dT).poly(dA-dT) in low and high salt: a 500 MHz 1H NMR study using one-dimensional NOE. 640 Aug 29

Arterial spasm was induced by application of calcium chloride to the adventitial surface of the rabbit common carotid artery in vivo. Sodium chloride (NaCl) was applied to the contralateral vessel as control. Vessels were fixed in situ by intravascular perfusion after 15 min, 1 hr, or 24 hr and prepared for light and scanning electron microscopy (SEM). With SEM, the luminal surface at the site of calcium application showed severe longitudinal folding accompanied by endothelial desquamation with extensive platelet deposition on exposed subendothelium. The luminal cross-sectional area was reduced by 53 +/- 19.5% after 15 min and by 44 +/- 12% after 1 hr as compared with the contralateral control. Furthermore, the luminal area at the site of calcium application was found to be reduced by 42 +/- 8% after 1 hr when compared with segments of the same vessel distal to the site of calcium application. Blood flow rate, as measured by electromagnetic flow probe, was not reduced. Vessels examined after 24 hr showed a significant increase in luminal cross-sectional area as compared with contralateral control vessels (136 +/- 70%). Control vessels (NaCl) showed no significant change in luminal cross-sectional area and no endothelial desquamation or platelet deposition after 15 min, 1 hr, or 24 hr. Examination of histologic sections showed calcium precipitation within the attached thrombus after 15 min with calcium deposits also adherent to the adjacent luminal aspect of the internal elastic lamina (IEL). By 24 hr, this precipitation extended throughout the media. Marked deposition of leukocytes was seen after 24 hr which showed a preferential attachment for areas of endothelial damage and discontinuity of IEL.
Exp Mol Pathol 1983 Oct
PMID:Intimal changes associated with arterial spasm induced by periarterial application of calcium chloride. 661 26

The flagellated protozoan Giardia lamblia has been grown only in highly complex media under reduced oxygen tension. Therefore, the organic and physiological requirements for in vitro attachment and short-term (12-h) survival of this organism were determined. In defined maintenance media, a thiol reducing agent (e.g., cysteine) was absolutely required for attachment and survival of this aerotolerant anaerobe. The crude bovine serum Cohn III fraction greatly stimulated attachment and survival. Attachment was decreased at a reduced temperature (24 degrees C as compared with 35.5 degrees C) and absent at 12 degrees C or below. Attachment and survival were strongly dependent upon pH and ionic strength, with optima at pH 6.85 to 7.0 and 200 to 300 mosmol/kg. Sodium chloride was better tolerated than KC1. Reduction of Ca2+ and Mg2+ to below 10(-8) M did not significantly affect attachment.
Mol Cell Biol 1982 Apr
PMID:Attachment of the flagellate Giardia lamblia: role of reducing agents, serum, temperature, and ionic composition. 711 Jan 36

Salt treatment of the cytoplasmic estradiol-receptor complex from chick oviduct induces a strong affinity of the complex for DNA-cellulose and phenyl-sepharose. This process is called activation. Binding to heparin- and lysozyme-sepharose is also observed with the untreated complex. But, the salt treatment, additional binding of the complex to these adsorbents is seen. The increased ability of the complex to bind to polyanions and polycations is destroyed by mild trypsination. The binding to the hydrophobic adsorbent is not affected by this treatment. Neither a change of the sedimentation constant nor of the size of the receptor protein is observed after salt treatment in the cold. After binding of the salt-activated estradiol-receptor complex to DNA-cellulose in the cold, an increase of its sedimentation constant and its size, as measured by density-gradient centrifugation and agarose gel chromatography, resp., becomes apparent. A similar phenomenon is observed after binding to DEAE-cellulose and to some extent after binding to heparin-sepharose. The nuclear complex seems to have the same sedimentation constant as the cytoplasmic complex eluted from DNA-cellulose. The sedimentation constant of the nuclear complex is not changed after DNA-cellulose chromatography. The cytoplasmic progesterone-receptor complex from the same tissue, i.e. the oviduct, does not show any change of size. Thus the well-known process of transformation can now be separated into 2 steps. (1) Activation of the estradiol-receptor complex for its binding to various adsorbents in vitro and probably to its acceptor site(s) in vivo. (2) Increase of receptor size. This second step seems to be a special property of the estradiol-receptor complex. Its physiological significance is unclear.
Mol Cell Endocrinol 1980 Dec
PMID:Transformation of the estrogen-receptor complex from chick oviduct in 2 steps. 720 34

Salt-dependent structural changes of rat liver chromatin isolated by an extraction procedure not involving shear and exogenous nucleases were investigated by sedimentation and light scattering methods. The effects observed are complex involving changes in the molecular weight and expansion. Between 0.1 M and 0.2 M (NH4)2SO4 where histone H1 is released, a fragmentation into molecules of half molecular weight is found which is accompanied by an expansion into a more extended conformation gradually increasing to 0.4 M (NH4)2SO2. The H1-free chromatin does not exhibit the reduction in molecular weight but undergoes this expansion. The original conformation is not reversible on re-decreasing the salt concentration to 0.1 M (NH4)2SO4.
Mol Biol Rep 1981 Aug 14
PMID:Physicochemical properties of salt-soluble, unsheared chromatin. Salt-dependent structural changes. 729 91

Salt dependent electrostatic effects play a central role in intermolecular interactions involving nucleic acids. In this paper, the finite-difference solution to the nonlinear Poisson-Boltzmann (NLPB) equation is used to evaluate the salt dependent contribution to the electrostatic binding free energy of the minor groove binding antibiotics DAPI, Hoechst 33258 and netropsin to DNA using detailed molecular structures of the complexes. For each of these systems, a treatment based on the NLPB equation accurately describes the variation of the experimentally observed binding constant with bulk salt concentration. A solvation formalism is developed in which salt effects are described in terms of three free energy contributions: the electrostatic ion-molecule interaction free energy, delta delta G degrees im; the electrostatic ion-ion interaction free energy, delta delta G degrees ii; and the entropic ion organization free energy, delta delta G degrees org. The electrostatic terms, delta delta G degrees im and delta delta G degrees ii, have both enthalpic and entropic components, while the term delta delta G degrees org is purely a cratic entropy. Each of these terms depends significantly on salt dependent changes in the counterion and coion concentrations around the DNA. In each of the systems studied, univalent ions substantially destabilize charged ligand-DNA complexes at physiological salt concentrations. This effect involves a salt dependent redistribution of counterions near the DNA. The free energy associated with the redistribution of counterions upon binding is dominated by the unfavorable change in the electrostatic ion-molecule interactions, delta delta G degrees im, rather than the change in the cratic entropy of ion organization, delta delta G degrees org. In addition, the observed slope of the salt dependence of the free energy is determined by electrostatic ion-molecule and ion-ion interactions as well as the cratic entropy of ion release. These findings are in contrast to models in which the cratic entropy of counterion release drives binding.
J Mol Biol 1994 Apr 29
PMID:Salt effects on ligand-DNA binding. Minor groove binding antibiotics. 751 53

The mouse surfeit locus is a tight cluster of at least six genes (surf-1 to -6), unrelated by sequence homology, whose unique organization is conserved in vertebrates. We show that the surf-4 coding sequence is conserved between mouse and human. Primary sequence analysis predicts that the mouse surf-4 protein contains seven transmembrane domains and a double lysine endoplasmic reticulum (ER) retrieval motif on the carboxyl terminus. Translation of the mouse surf-4 cDNA in vitro resulted in the production of a 30 kDa membrane protein. Salt and detergent extraction procedures showed that the surf-4 protein associated tightly with the microsomal membranes. Proteolysis protection of 14 and 3 kDa fragments indicates that the surf-4 protein contains at least two membrane spanning domains: this is consistent with the proposed topology. Addition of the c-Myc epitope into three different regions of the surf-4 protein resulted in transfectants that expressed a myc-tagged protein. Immunofluorescence analysis of the three surf-4 myc chimeras yielded a cytoplasmic staining pattern. Consistent with the presence of the ER retrieval motif, the surf-4 myc protein was not detected at the plasma membrane. A model for the proposed structure of the surf-4 protein is presented.
Mol Membr Biol
PMID:The surf-4 gene encodes a novel 30 kDa integral membrane protein. 754 Sep 14


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