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Query: UNIPROT:P06889 (Mol)
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The detergent-soluble extract of rat ovary plasma membranes contained a Gs protein of about 100 kDa as shown by its elution behavior on a Bio Gel A-1.5m column. However, the cell membranes exposed to hCG (37 degrees C, 15 min) contained in addition a higher molecular weight Gs protein complex of 300 kDa comprised of human chorionic gonadotropin (hCG) receptor (hCGR) and Gs. The complex bound with an affinity column of GTP-Sepharose and could be released with Gpp(NH)p and GTP inhibited this binding. The presence of the hCGR in the complex was shown by its binding to 125I-hCG. Furthermore, GTP inhibited the binding of hCG to the complex. These results indicate the presence of hCGR and Gs protein complex in the hCG-treated membranes. hCGR and Gs protein were individually purified and reconstituted into phospholipid vesicles. The protein-phospholipid vesicles showed saturation kinetics of binding of 125I-hCG and 3H-Gpp(NH)p. Incubation of phospholipid vesicles with hCG resulted in a 2-3-fold increase in the binding of 3H-Gpp(NH)p and GTPase activity. Activation of Gs protein was dependent on the length of incubation and the hormone concentration. Deglycosylated hCG was about 10 times less potent than hCG suggesting a role of carbohydrates of hCG in inducing hCG-Gs protein interactions. The data with the in vitro reconstitution system rule out the involvement of a carbohydrate-binding lectin in the function of the hormone.
Mol Cell Endocrinol 1991 Sep
PMID:Human choriogonadotropin-induced coupling of receptor and Gs protein and the effect of hormone deglycosylation. 195 70

Four isoforms of glycosylated prolactin (G-pPRL) were isolated from porcine pituitary glands by affinity chromatography and concanavalin A-Sepharose, based upon differences in their affinity for the lectin. Structural analysis indicated differences in the carbohydrate units of the four G-pPRLs. N-glycanase treatment cleaved the oligosaccharide from the G-pPRLs, establishing N-linked glycosylation. The binding of G-pPRLs to receptors from lactating rabbit mammary glands was only 3-8% that of nonglycosylated pPRL (NG-pPRL). The immunological crossreactivity of the G-pPRLs varied from 36 to 65% that of NG-pPRL. When tested in the pigeon crop sac bioassay, G-pPRLs were only 11-40% as active as NG-pPRL. The metabolic clearance rate of one of the G-pPRLs was slower and another faster than that of NG-pPRL. We conclude that there are several forms of G-PRL of variable immuno- and bio-potencies in the porcine pituitary, and that the current radioimmunoassay for the hormone does not measure the actual bioactivity.
Mol Cell Endocrinol 1991 Sep
PMID:Isolation and biochemical properties of four forms of glycosylated porcine prolactin. 195 78

Rat androgen-binding protein (rABP), human testosterone-binding globulin (hTeBG) and rabbit (rb) TeBG are heterodimeric proteins. The source of the heterogeneity arises from the differential glycosylation of a common protein core. This glycosylation results in a heavy subunit (more glycosylation) and a light subunit (less glycosylation). Glycosylation is one factor responsible for multiple charged species seen when rABP, hTeBG, and rbTeBG are analyzed by two-dimensional gel electrophoresis. Enzymatic digestion with the endoglycosidase, peptide: N-glycosidase F indicated that all three proteins have asparagine (Asn)-linked oligosaccharides as their major glycan substituent. Treatment with exoglycosidases provided evidence for terminal sialic acid, galactose and mannose and N-acetylglucosamine residues. About 16-22% of the mass of the heavy subunit and about 8-14% of the mass of the light subunit is contributed by carbohydrate. Serial lectin chromatography indicated that rABP is glycosylated differently from hTeBG and rbTeBG. About 40% of the rABP contains tri and tetraantennary complex oligosaccharides, while only about 20% of the hTeBG and TeBG from pregnant rabbits contains these types of glycans. About 9% of the TeBG from male rabbits bears these types of oligosaccharides. All of the biantennary complex oligosaccharides on rABP are fucosylated on the chitobiose core, but only 8% of those on hTeBG and none of those on rbTeBG are fucosylated in this manner. All three proteins are glycosylated at more than one site. The data indicate that the proteins may have more than one type of oligosaccharide on them. It is likely that differences in glycosylation are responsible for different physiological roles of the proteins.
J Steroid Biochem Mol Biol 1991
PMID:Analysis of the oligosaccharides on androgen-binding proteins: implications concerning their role in structure/function relationships. 195 77

The third component of complement (C3) plays key roles in complement activation of both the classical and alternative pathways. The liver is the major site of C3 synthesis; monocytes, B-lymphocytes and leukemic cell lines of the myeloid lineage also synthesize C3. Here we report that the C3 gene is inactive in fresh T-cells, but active in T-cells treated with the lectin phytohemagglutinin (PHA). Northern blot hybridization studies show that PHA-activated T-cells and all the T-cell lines tested express the 5.3 kb RNA transcript reported for C3 in HepG2, a hepatoma cell line, and monocytes. We used radioimmune precipitation followed by polyacrylamide gel electrophoresis to show that PHA-stimulated T-cells and T-cell lines, which are not infected with the human T-lymphotropic virus (HTLV), synthesize and release C3 proteins with molecular masses of 185, 115 and 80 kD; HTLV-infected T-cell lines release C3 proteins of 170, 115 and 70 kD. In contrast, monocytes produced C3 proteins of 115 and 70 kD similar to the serum form of this protein. The role of T-lymphocyte C3 and the implications of HTLV-infection are discussed.
Mol Immunol 1990 Mar
PMID:Synthesis of the third component of complement (C3) by lectin-activated and HTLV-infected human T-cells. 197 21

cDNAs coding for rat ovarian luteinizing hormone receptor analogs lacking three of the leucine repeats were detected in a library which had been prepared from rat luteal tissue undergoing human chorionic gonadotropin-induced luteinization. These leucine repeats correspond to amino acids 206-267 and contain the portion of the receptor that is homologous to the soybean lectin. The cDNA library also contained a receptor analog lacking amino acids 321-700 which code for the transmembrane domain. S-1 mapping suggests that this latter form constitutes approximately half of all receptor-related mRNA.
Mol Cell Endocrinol 1990 Jul 09
PMID:Cloning of rat lutropin (LH) receptor analogs lacking the soybean lectin domain. 197 54

Tissue-binding specificity of the type-3 fimbriae of pathogenic enteric bacteria was determined using frozen sections of human kidney. A wild-type Klebsiella sp. strain and the recombinant strain Escherichia coli HB101(pFK12), both expressing type-3 fimbriae, as well as the purified type-3 fimbriae effectively bound to sites at or adjacent to tubular basement membranes, Bowman's capsule, arterial walls, and the interstitial connective tissue. Bacterial adherence to kidney was decreased after collagenase treatment of the tissue sections. Recombinant strains expressing type-3 fimbriae specifically adhered to type V collagen immobilized on glass slides, whereas other collagens, fibronectin or laminin did not support bacterial adherence. In accordance with these findings, specific binding of purified type-3 fimbriae to immobilized type V collagen was demonstrated. Specific adhesion to type V collagen was also seen with the recombinant strain HB101(pFK52/pDC17), which expresses the mrkD gene of the type-3 fimbrial gene cluster in association with the pap-encoded fimbrial filament of E. coli, showing that the observed binding was mediated by the minor lectin (MrkD) protein of the type-3 fimbrial filament. The interaction is highly dependent on the conformation of type V collagen molecules since type V collagen in solution did not react with the fimbriae. Specific binding to type V collagen was also exhibited by type-3 fimbriate strains of Yersinia and Salmonella, showing that the ability to use type V collagen as tissue target is widespread among enteric bacteria.
Mol Microbiol 1990 Aug
PMID:Type V collagen as the target for type-3 fimbriae, enterobacterial adherence organelles. 198 Jul 13

In this report we introduce a simple, fast, and reliable method to prepare whole cell or nuclear extracts from small numbers of cells. These extracts were used to study transcriptional activation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) in vitro. Our results revealed that the time courses of activation of extracts derived from cells stimulated with the mitogenic lectin phytohemagglutinin (PHA) or with the tumor promoter phorbol 12-myristate 13-acetate (PMA) are different. PMA induces a rapid onset of increased in vitro transcription from the HIV-1 LTR, while PHA causes a slow and sustained response. The biochemical relevance of protein synthesis inhibition by cycloheximide treatment of cells was investigated. In these studies, PMA induction of a change in in vitro transcriptional activity is not dependent on protein synthesis. Cycloheximide alone is insufficient to induce activation. Oligonucleotide-mediated site-directed mutagenesis demonstrated that mutation of the TATA box in the LTR ablated initiation of both basal-level transcription and activation by extracts from cells stimulated with PMA. Surprisingly, mutation of both kappa B sites in the LTR reduced but did not eliminate the in vitro response to extracts prepared at early time points after PHA or PMA stimulation of Jurkat cells. The reduction was greater in extracts derived from cells treated with PMA. Deletion analysis of the HIV-1 LTR revealed at least one region (-464 to -252) capable of suppressing in vitro transcription in extracts from Jurkat cells stimulated by PMA. This result is consistent with early studies of the HIV-1 LTR in transient transfection assays. We therefore have been able to observe distinct regulatory events at early time points after cells are exposed to agents known to induce transcription of both the HIV-1 LTR reporter gene constructs and the HIV-1 provirus itself.
Mol Cell Biol 1991 Apr
PMID:An in vitro transcription analysis of early responses of the human immunodeficiency virus type 1 long terminal repeat to different transcriptional activators. 200 86

Preliminary diffraction data collected on peanut agglutinin (PNA) crystals grown in the presence of N6-benzylaminopurine (BAP) indicate a monoclinic cell (P2) with a = 67.0 A, b = 35.2 A, c = 65.8 A and beta = 68.6 degrees. This is the first example of a legume lectin crystallized with a bound phytohormone. Crystals of PNA grown previously in the presence of lactose had an orthorhombic space group (P2(1)2(1)2) with a = 128.8 A, b = 126.0 A and c = 76.1 A and one tetramer per asymmetric unit. The Vm value for the PNA-BAP crystals is 2.62 A3/Da, assuming one monomer of PNA per asymmetric unit. Thus, while the PNA-lactose complex crystallized as tetramers, the PNA-BAP complex has, at most, dimers in the crystal. These results indicate that BAP, a naturally occurring phytohormone, can modify the quaternary structure of PNA by dissociation and change its carbohydrate valence.
J Mol Biol 1991 May 20
PMID:Crystallization and preliminary X-ray analysis of peanut agglutinin-N6-benzylaminopurine complex. 203 51

Genetic analysis in Dictyostelium discoideum has identified regulatory genes which control the developmental expression of the discoidin lectin multigene family. Among these, the drsA mutation is a dominant second-site suppressor of another mutation, disB, which has the discoidinless phenotype. We now demonstrate a novel mechanism by which the drsA allele exerts its suppressive effect on the disB mutation. Interestingly, drsA does not merely bypass the disB mutation and restore the wild-type pattern of lectin expression. Rather, drsA mutant cells have high levels of discoidin lectin synthesis during growth but do not express lectins during aggregation. In contrast, wild-type cells only express lectin protein during the aggregation period of development. Phenocopies of the drsA mutation show a pattern of discoidin expression similar to that seen in the bona fide mutant. These data suggest that there may be a mechanism of negative feedback, resulting from the high levels of discoidin lectin made during growth, which inhibits further discoidin lectin expression during development. Northern (RNA) analysis of developing drsA mutant cells shows that these cells contain high levels of discoidin mRNA, although no discoidin lectin protein is being translated from these messages. Therefore, expression of the discoidin gene family can be controlled at the level of translation as well as transcription.
Mol Cell Biol 1991 Jun
PMID:Translational control of discoidin lectin expression in drsA suppressor mutants of Dictyostelium discoideum. 203 25

Rat alveolar type II pneumocytes, in situ, label with Maclura pomifera agglutinin (MPA), a plant lectin that recognizes alpha-galactosyl oligosaccharide residues of glycoproteins and glycolipids. To study the glycoproteins recognized by the lectin, MPA lectin affinity chromatography was used to isolate a novel glycoprotein, pneumocin, from type II and whole rat lung cell membranes. Pneumocin isolated from adult rat lungs was a non-disulfide-linked sialoglycoprotein with an Mr of 165 kD. Asparagine-linked oligosaccharides contributed 5 to 10% to the Mr. Two-dimensional chymotryptic peptide maps of pneumocin isolated from whole lung membranes and type II cells were similar. The glycoprotein partitioned in the detergent phase on Triton X-114 phase separation. Murine monoclonal antibodies developed against the purified glycoprotein localized on apical membranes of type II pneumocytes in situ. The antibodies did not label type I cells or lamellar bodies but labeled luminal surfaces of vesicular structures of type II cells. Isolated type II cells labeled with antibodies after 1 d in culture but showed significantly less staining of cells after 4 d of culture. These observations demonstrate that pneumocin is a cell surface sialoglycoprotein marker of type II cells. Western blot analysis of liver and kidney cell membranes suggest that related glycoproteins may also be present in those tissues. The isolation technique and monoclonal antibodies should permit further characterization and functional studies of the glycoprotein.
Am J Respir Cell Mol Biol 1991 Jun
PMID:Isolation and partial characterization of pneumocin, a novel apical membrane surface glycoprotein marker of rat type II cells. 205 90


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