PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Transcortin”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1989

Transcortin biosynthesis and intracellular distribution of rat liver polyribosomes synthesizing transcortin.

Transcortin biosynthesis in rat has been examined using liver slices technique. The incorporation of 14C-labeled amino acids into the anti-transcortin-precipitable material of liver slices has been measured and compared with that of serum transcortin. It was shown that liver synthesized transcortin with an apparent mol. wt of 66 kDa on SDS-electrophoresis which co-migrated with authentic rat serum transcortin. In order to determine an intracellular distribution of transcortin synthesizing polyribosomes, the binding character of [125J]anti-transcortin-IgG to free and membrane-bound rat liver polyribosomes has been studied. It was shown that after incubation of [125J]anti-transcortin-IgG with liver membrane-bound polyribosomes, the radioactivity was associated with the discrete polyribosome fraction in heavy polyribosome region. In similar experiments the radioactivity of [125J]anti-transcortin-IgG bound to the free polyribosomes was distributed throughout the polyribosome region. The results of our experiments obviously demonstrated that serum transcortin was synthesized exclusively on membrane-bound polyribosomes of rat liver; free polyribosomes were devoid of detectable antigenic material able to bind antibodies to transcortin.

Animals↗
PubMed1991

Transcortin in rat kidney: subcellular distribution of transcortin-synthesizing polyribosomes.

The [3H]corticosterone-transcortin complexes from kidney cytosol show elution positions on DEAE-cellulose identical to serum transcortin. The incorporation of 14C-labeled amino acids into anti-transcortin-precipitable material of kidney slices has been measured and compared with that of serum transcortin. It was established that kidney synthesized transcortin with an apparent molecular weight of 66 kDa on SDS-electrophoresis which resembles serum corticosteroid-binding globulin. Studies on the binding of [125I]anti-transcortin-IgG to membrane-bound rat kidney polyribosomes revealed an association of [125I]anti-transcortin-IgG with a discrete polyribosome fraction in the heavy polyribosome region; free polyribosomes were devoid of antigenic material able to bind antibodies to transcortin.

Animals↗
PubMed1991

On the functional form of transcortin-recognizing subunit of transcortin membrane receptor.

Complex formation between transcortin and the 20 kDa sialoglycoprotein from the plasma membrane of human decidual endometrium (presumably a transcortin-recognizing subunit of transcortin membrane receptor) was studied using cross-linking reagents. The action of 1,5-difluoro-2,4-dinitrobenzene (DFDNB) on a solution of 125I-labelled 20 kDa sialoglycoprotein and unlabelled transcortin resulted in the formation of two 125I-containing containing species that corresponded to covalently linked complexes of one transcortin molecule and either 2 or 4 molecules of the labeled membrane sialoglycoprotein. Only the latter complex was observed when the endometrium membranes were incubated with [125I]transcortin and treated with DFDNB. This suggests that the functional form of transcortin-recognizing subunit of the membrane receptor is a tetramer.

Cell Membrane↗
PubMed1989

Study of the transcortin binding to human endometrium plasma membrane.

Transcortin complexed with progesterone was shown to bind specifically to the plasma membrane of human decidual endometrium. The binding reaction was characterized by a high affinity (an apparent Kd value was (1.0 +/- 0.2).10(-10) mol/l) and high selectivity: such human serum proteins as albumin, orosomucoid, transferrin, thyroxine-binding globulin and sex hormone-binding globulin did not compete with transcortin for the membrane binding sites. Transcortin binding to the membrane was steroid-dependent: transcortin-cortisol complex bound to the membranes substantially more weakly than transcortin-progesterone, and specific binding of transcortin devoid of steroid was not detected. Using a radioimmunoassay, we have measured the concentration of endogenous transcortin in highly purified membrane preparations solubilized with sodium cholate. It was found that an extensive washing of decidual strips with a physiological buffer prior to the membrane isolation resulted in a decrease of the endogenous transcortin level along with an increase of the specific membrane binding of exogenous 125I-labeled transcortin. Affinity chromatography on immobilized transcortin was used to isolate transcortin-binding components from 125I-labeled, cholate-solubilized plasma membrane of decidual endometrium. Along with lipid components, the structure of which was not investigated, a 125I-labeled transcortin-binding sialoglycoprotein with a minimal Mr of 20.0 +/- 1.5 kDa and a pI of approx. 3.3 was detected. In the presence of transcortin, this sialoglycoprotein could be precipitated with a monospecific antitranscortin antiserum. Using hydroxylapatite as a separating agent, the interaction of transcortin and the membrane sialoglycoprotein in model systems containing the two proteins and various steroid hormones was studied. It was found that the membrane sialoglycoprotein displayed a higher affinity for transcortin-progesterone than for transcortin-cortisol (the Kd values were, respectively, 2.10(-11) and 7.10(-11) mol/l) and it did not bind transcortin complexed with testosterone.

Blood Proteins↗
PubMed1985

Human transcortin synthesis by a cell-free translation of hepatic mRNA.

To evaluate the site of synthesis and to characterize the translated transcortin, poly (A)-containing RNA (mRNA) from human liver was translated in a cell-free system derived from rabbit reticulocyte lysate. The in vitro synthesized product was identified as transcortin by immuno-precipitation with its specific antiserum. This translated transcortin could be displaced from the antibody by unlabeled purified transcortin obtained from plasma. Furthermore, when the translation mixture was applied to a cortisol-Sepharose column, the translated transcortin was bound to the matrix in a specific manner, indicating that this product binds to cortisol. The molecular weight of the translated transcortin was estimated to be 45,700 by its mobility in sodium dodecyl sulfate polyacrylamide gel electrophoresis, while that of plasma transcortin was 53,800. The difference in molecular weight between the translated transcortin and plasma transcortin was probably due to the presence of pre-sequence (signal peptide) in addition to the absence of carbohydrate moiety in the former. In conclusion, human liver mRNA directed the synthesis of transcortin, and the translated transcortin binds to cortisol in spite of the absence of carbohydrate moiety.

Animals↗
PubMed1988

Evidence for the involvement of the transcortin carbohydrate moiety in the glycoprotein interaction with the plasma membrane of human placental syncytiotrophoblast.

We have studied the interaction of human transcortin and the pregnancy-associated transcortin variant with the microvesicular membrane fraction derived from the human placental syncytiotrophoblast. Two classes of specific binding sites for these glycoproteins were found in this membrane preparation. One of these displays a relatively high binding capacity, Bmax = 140 +/- 60 fmol transcortin per mg membrane protein, and a significantly higher affinity for transcortin, Kd = (1.6 +/- 0.6).10(-10) mol/l, than for the pregnancy-associated variant, Kd = (4.5 +/- 1.2).10(-9) mol/l. On the contrary, another class of the binding sites, occurring in the membranes at a far lower concentration: Bmax = 3.0 +/- 2.2 fmol transcortin per mg membrane protein, shows a higher affinity for the pregnancy-associated transcortin variant, Kd = (3.3 +/- 2.0).10(-12) mol/l, than for normal transcortin, Kd = (2.5 +/- 0.7).10(-11) mol/l. Since the pregnancy-associated variant differs from normal transcortin with respect to its carbohydrate structures only (Avvakumov, G.V. and Strel'chyonok, O.A. (1987) Biochim. Biophys. Acta 925, 11-16), the results of the present work suggest that the transcortin carbohydrates are directly involved in the specific interaction of this serum hormone-binding globulin with the plasma membrane of the placental syncytiotrophoblast.

Binding, Competitive↗
PubMed1986

Comparative study of primates' transcortin: immunoreactivity and steroid-binding activity.

To investigate the phylogenic aspect of transcortin (corticosteroid-binding globulin, CBG), the immunoreactivity of transcortin with anti-human transcortin antiserum was studied in primates. The anti-human transcortin antibody was recognized by plasma proteins obtained from Catarrhini, taxonomically the most evolved monkey group. The immunoreactivity was not observed in plasma obtained from Platyrrhini and Prosimiae, classified as less evolved monkey groups than Catarrhini. Though comparison of immunoreactivity among different classes of Catarrhini was difficult because of non-parallelism of their displacement curves, displacement of 125I-labelled human transcortin from the antiserum by 1:10 and 1:100 diluted plasma was highest in human followed by Pongidae, Cercopithecoidea. The immunoreactivity of thyroxine-binding globulin (TBG) with anti-human TBG antiserum was also examined. The anti-human TBG antibody was only recognized in plasma from Pan (anthropoid ape) among Pongidae, highly evolved monkeys among Catarrhini. The existence of immunoreactive transcortin and TBG to respective human protein antibody in the highly evolved ape agreed well with the cladogenetic division of primate species delineated by Goodman and Moore (1971). Cortisol-binding activity of transcortin was detected in all monkeys except three, tafted capuchin monkey, night monkey and cotton-headed tamarin, which belong to Platyrrhini. The absence of cortisol-binding activity in these animals might be attributed to high levels of endogenous cortisol and low cortisol-binding capacity of transcortin. It is speculated that the structure of the immunoreactive site in transcortin could be modified by evolution without affecting the biologically important site, the site for cortisol binding.

Animals↗
PubMed1986

Transcortin and vitamin D-binding protein levels in mouse serum.

The influence of age, sex and strain on the serum concentration of transcortin (corticosteroid-binding globulin) and vitamin D-binding protein (DBP) in mice was investigated. The effect of age was studied in two strains, C57BL/6JPfd and BALB/cmHeAPfd. The concentration of transcortin and DBP increased with age. In young animals the concentration of each protein showed a significant strain difference, which disappeared in older mice for DBP, but not for transcortin. In 7-day-old animals, no sex difference was observed for either protein, but in older animals a clear sex difference was found for transcortin. Adult males tended to have somewhat higher levels of DBP than adult females, but this difference was significant only on day 70. The variation in transcortin and DBP levels was further investigated in a large number of mouse strains. The DBP concentration did not markedly vary among strains (5.98-9.65 mumol/l in males and 5.08-8.85 mumol/l in females). Transcortin, however, showed marked strain variations, ranging from 0.72 to 2.06 mumol/l in males and from 1.02 to 4.55 mumol/l in females and there was a significant correlation (r = 0.66, n = 26, P less than 0.001) between the mean transcortin levels in males and females of different strains. Interstrain variation was much higher than intrastrain variation or variation among related strains, suggesting that the transcortin concentration is largely controlled by genetically determined factors. There was a significant correlation (r = 0.82, n = 9, P less than 0.01) between the mean corticosterone and transcortin concentrations (measured at 21.00 h).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMedDate not supplied

[Identification of transcortin-synthesizing polyribosomes in the rat liver].

Transcortin biosynthesis in rats has been examined using liver slices technique. The incorporation of [14C]-labelled amino acids into the anti-transcortin-precipitable material of liver slices has been measured and compared with that of serum transcortin. It was shown that liver synthesized transcortin with an apparent molecular weight of 66 kDa on SDS-electrophoresis which co-migrated with authentic rat serum transcortin. In order to determine an intracellular distribution of transcortin-synthesizing polyribosomes, the binding character of [125J] anti-transcortin-IgG to free and membrane-bound rat liver polyribosomes has been studied. It was shown that after incubation of [125J] anti-transcortin-IgG with liver membrane-bound polyribosomes, the radioactivity was associated with the discrete polyribosome fraction in the heavy polyribosome region. In similar experiments the radioactivity of [125J] anti-transcortin-IgG bound to free polyribosomes was distributed throughout the polyribosome region.

Animals↗
PubMedDate not supplied

[Effect of transcortin on the corticosterone-transforming activity of cytosol from the rat liver].

The study of transcortin role in 3H-corticosterone metabolism has shown that transcortin of blood plasma from rats bearing Walker carcinosarcoma preserves the hormone conversion to dihydrocompounds 4 time less intensively than transcortin taken from healthy rats. Inactivated transcortin exerts no effect on the rate of formation of 5 beta-metabolites. Under the influence of homogeneous transcortin samples, a decrease in the content of 5 beta-reduced corticosterone metabolites is revealed to occur depending on transcortin concentration in the system. It is shown that in incubation systems where hormone is in the bound state the metabolism preserving capacity of transcortin depends on the temperature degree. The transcortin activity on corticosterone metabolism is supposed to be closely related to the intensity of its complexing with transcortin.

Animals↗
PubMed1987

Properties and serum levels of pregnancy-associated variant of human transcortin.

The amino acid composition, N- and C-terminal amino acid sequences, and the basic physicochemical and immunochemical properties of the recently discovered pregnancy-associated molecular variant of human transcortin (Strel'chyonok, O.A., Avvakumov, G.V. and Akhrem, A.A. (1984) Carbohydr. Res. 134, 133-140) have been found to be identical to those of transcortin from normal donor serum. This suggests the identity of polypeptide moieties of the two glycoproteins. The transcortin variant has a lower isoelectric point (3.5-4.1) than normal transcortin (3.6-4.2), and different electrophoretic mobility in low-porosity polyacrylamide gel (one band versus two for normal transcortin). These differences can be reasonably explained by different organization of the carbohydrate moieties of these glycoproteins due to diverse post-translational modification of a single polypeptide chain. The levels of transcortin variant in the maternal venous serum throughout normal gestation (447 donors in all) and on the fifth day after delivery, as well as in umbilical cord serum and extracts of term placenta, have been measured by a radioimmune assay. Analysis of the data obtained allowed us to conclude that the biosynthesis of pregnancy-associated transcortin variant occurs in some organ of the maternal organism rather than in the feto-placental system, and it is a characteristic of pregnancy as a unique physiological state of the female organism rather than a phenomenon caused by individual features of certain women. We assume that the transcortin variant takes part in the guided transport of corticosteroids and/or progestins into some tissues that develop in the course of gestation.

Amino Acid Sequence↗
PubMed1976

[Protein binding glucocorticoid hormones (transcortin) during peri-and postnatal ontogenesis and pregnancy in rats].

The constants of association and the energy of interaction between transcortin and cortisol, the binding ability and other characteristics of transcortin have been studied in the embryos, sexually immature and mature young and old females, females on the 14th and 21st days of pregnancy, immature and mature males. The constant of association in all the groups amounted to ca. 10(8) and the energy of interaction ca. 10 Cal/mole. The embryos and immature rats of both sexes are characterized by relatively low levels of the binding ability of transcortin. During the sexual maturation, the level of transcortin increased--insignificantly in males and markedly in females. The level of transcortin in the latter remained almost invariable during pregnancy and senescence. By the electrophoretic and sedimentation properties transcortin was the same in different groups. The high level of transcortin during pregnancy corresponded to the high level of hormones bound by transcortin, the level of these hormones in the embryos being much lower than in the mother.

Age Factors↗
PubMed1986

Phylogenetic study of transcortin using monoclonal antibodies.

We produced monoclonal antibodies that recognise three distinct epitopes of human transcortin. These epitopes are present on transcortin of humans with normal and altered transcortin levels, as well as on a variant with lower affinity for cortisol. One epitope is present on transcortin of Old World Monkeys and apes, the others are only present on transcortin of apes. The epitopes are not present on transcortin of other species. These results indicate that human transcortin contains a highly evolved and a more conserved part.

Animals↗