Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carboxypeptidase E (CPE) is involved in the biosynthesis of most neuropeptides and peptide hormones. Until recently, CPE was the only intracellular carboxypeptidase thought to be involved in neuroendocrine peptide processing. However, the finding that fat/fat mice, which have a mutation within the CPE gene that inactivates the enzyme, are capable of a reduced amount of insulin processing suggests that another carboxypeptidase is present within the secretory pathway. We have detected a CPE-like enzyme, designated CPD, which has many properties in common with those of CPE. Like CPE, CPD is a metallocarboxypeptidase that has a pH optimum of 5.5-6. The Km and Kcat values for a series of short peptide substrates show only minor differences between CPD and CPE. Several active site-directed inhibitors also show generally similar potency toward the two enzymes, although guanidinoethylmercaptosuccinic acid is approximately 10-fold more potent, and hippuryl-Arg is approximately 100-fold more potent as an inhibitor of CPD than of CPE. A major difference between the two enzymes is the molecular masses; CPE is 50,000-56,000, whereas CPD is approximately 180,000. Also, CPD does not elute from a substrate affinity column when the pH is raised to 8, which elutes CPE, although CPD can subsequently be eluted by arginine. Both CPE and CPD are present in purified bovine anterior pituitary secretory vesicles, but the tissue distribution of CPD is more uniform than that of CPE. Antisera to the N- and C-terminal regions of CPE do not recognize CPD. The partial N-terminal amino acid sequence of bovine CPD shows 30-40% homology with an N-terminal region of bovine and rat CPE and 70% homology with a duck protein known as gp180, a hepatitis B virus particle binding protein that shows 47% homology to CPE. Taken together, these results suggest that CPD is a novel secretory pathway enzyme that may be the bovine homologue of gp180.
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PMID:Purification and characterization of carboxypeptidase D, a novel carboxypeptidase E-like enzyme, from bovine pituitary. 755 30

A mutation in the tumor suppressor p53 gene resulting in an Arg-->Ser substitution in position 249 is found frequently in human hepatocellular carcinomas associated with hepatitis B infection and with aflatoxin exposure. To determine the significance of this mutation in an in vivo experimental model using transgenic mice, we introduced a two-nucleotide change in the mouse p53 gene at amino-acid position 246, which is equivalent to position 249 in human p53, by the recombinant polymerase chain reaction mismatched primer method. This p53 mutation resulted in the same change, an Arg-->Ser substitution, as in the human p53 gene at position 249. We now report that the protein product of this mutant mouse p53ser246 had properties similar to those of the wild-type protein when tested by binding to (i) monoclonal antibodies PAb246 and PAb240, ii) simian virus 40 large T antigen, and (iii) heat-shock protein. However, it had mutant-type transforming properties when tested for colony formation with an osteosarcoma cell line. It was not active, as is wild-type p53, in transcription activation of the muscle creatine kinase promoter. These properties are the same as those found in the p53trp248 product of the p53 mutation associated with the Li-Fraumeni syndrome. Although less is known about the human p53ser249 product associated with hepatocellular carcinoma, the mutant murine p53ser246 protein shares the known properties of the human gene product.
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PMID:Characterization of a murine p53ser246 mutant equivalent to the human p53ser249 associated with hepatocellular carcinoma and aflatoxin exposure. 760 78

Using PCR, we have cloned antibody heavy and light chain variable region (VH and VL) coding sequences specific for a recombinant hepatitis B virus surface antigen (HBsAg) and assembled these for expression as single-chain Fv (scFv) fragments in Escherichia coli periplasm using the ompA signal peptide. The vectors also encoded N- or C-terminal His6 extensions to allow for the purification of the expressed proteins using immobilized metal affinity chromatography (IMAC). We found that the VH-linker-VL configuration of the scFv was not exported to the periplasm but remained associated with cellular insoluble material, from which it could be extracted, renatured to its active form by gentle dialysis and purified using IMAC. The molecular size of the scFv suggests that the ompA signal peptide was not processed. Based on previous reports, we hypothesized that the arginine in framework 1 (FR1) of the VH might interfere with translocation to the periplasm by means of the signal peptide. Because no arginines are present in FR1 of VL, we reversed the order of the V-regions in the scFv and observed efficient export of the active scFv to the periplasm. Furthermore, when the arginine in FR1 of VH was mutated to glycine in the original VH-linker-VL construct, active scFv was also exported to the periplasm. Thus, exposed positive charges near the signal peptide may account for at least some of the often-encountered difficulties in bacterial scFv expression.
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PMID:Variable region sequence modulates periplasmic export of a single-chain Fv antibody fragment in Escherichia coli. 761 89

Amino acid substitutions at several positions in the surface antigen (HBsAg) of hepatitis B virus (HBV) in natural isolates and the products of recombinant DNA molecules have identified important residues for cross-reaction with specific antibodies (anti-HBs) and the induction of antibodies with certain serological specificities. In a further group of mutants described here, cysteine residues in a region believed to be significant of the a epitope have been changed to serines. Of the three adjacent cysteine residues at positions 137, 138 and 139, mutation of either of the flanking residues reduced cross-reactivity with polyclonal anti-HBs, while alteration of the central residue was relatively well-tolerated. Mutation of cysteine 149 to serine or of glycine 145 to arginine (imitating naturally occurring mutants), lysine, or glutamatic acid all led to loss of cross-reactivity with polyclonal antisera.
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PMID:Mutations of some critical amino acid residues in the hepatitis B virus surface antigen. 763 5

Molecular genetic studies have revealed that the human hepatitis B viral (HBV) Pol protein, a polypeptide of about 94 kDa, contains four domains. These are the 5'-terminal protein, spacer, RNA reverse transcriptase/DNA polymerase, and RNase H, respectively, from the amino (N) to carboxy (C) terminus. No evidence indicates as yet the involvement of a specific protease in cleaving the Pol protein or the presence of protease-cutting sites in the Pol protein. An in vitro-translated Pol protein was shown to be cleaved by purified thrombin but not in the presence of its inhibitor, hirudin. Two thrombin-cutting sites, spanning 194 amino acids, were then deduced by thrombin digestion of Pol protein with various lengths of C-terminal deletion. These two putative cutting sites, one located in the spacer region and the other in the beginning of the polymerase region, were found to be conserved at similar positions in the Pol protein of all hepadnaviruses. By using a novel method called the LacZ localization assay (LLA), it was demonstrated that a tripartite fusion protein containing the nucleus localization sequence (NLS) of SV40 large T Ag, the putative thrombin cutting sequence (Ile-Arg-Ile-Pro-Arg320-Thr) of HBV Pol protein and the full length beta-galactosidase of E. coli, exhibited a lower percentage (approximately 53%) of targeting into the nucleus of transfected hepatoma cells when compared with a similar tripartite protein containing a single mutation (Arg320 residue into Trp320) of HBV Pol protein (approximately 78%) or with a bipartite protein of SV40 NLS-beta-galactosidase (approximately 90%). These results indicate that the putative thrombin-cutting site in the spacer region of HBV Pol protein could be cleaved by a cellular protease resulting in the separation of NLS sequence from the beta-galactosidase and rendering a lower frequency of X-gal staining in the nucleus.
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PMID:Demonstration of the presence of protease-cutting site in the spacer of hepatitis B viral Pol protein. 773 Apr 38

Termination mutations in the precore open reading frame of hepatitis B virus (HBV) variants with defective hepatitis B e antigen (HBeAg) production have been demonstrated in both infected patients who have seroconverted to anti-HBe and those with fulminant hepatitis B. A donated plasma sample was found to be positive for the hepatitis B surface antigen, but negative for both HBeAg and anti-HBe. The HBV DNA titer in the plasma was estimated to be 32 pg/ml, and circulating virus-like particles were observed by electron microscopy. The entire nucleotide sequence of the virus was determined and at least 7 nucleotides were found to be unique when compared with previously reported sequences. These nucleotides created no termination codon in the precore/core, pol, preS/S and HBx open reading frames. The deduced amino acid substitutions were 28 Arg--Gln, 94 His--Tyr, 131 Val--Ile and 132 Phe--Tyr of HBx and 715 Met--Val and 789 Asp--Asn of pol. Furthermore, the precore and core/pregenome promoter contained altered 1764 A, 1766 T and 1768 A. Therefore, mutations in regions other than the precore open reading frame can cause defective HBeAg production.
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PMID:Mutations in the transcriptional regulatory region of the precore and core/pregenome of a hepatitis B virus with defective HBeAg production. 785 32

Hepadnavirus replication requires the concerted action of the polymerase and core proteins to ensure packaging of the RNA pregenome and DNA maturation. The arginine-rich C terminus of the core protein plays an essential role in both of these steps while being dispensable for nucleocapsid formation. In an attempt to identify other functional domains of the core protein, we performed a series of trans-complementation experiments analyzing the ability of duck and human hepatitis B virus (DHBV and HBV) core protein subunits to support the replication of a core-defective DHBV genome. Plasmids expressing the N-terminal amino acids 1 to 67 or the remaining C-terminal portion, amino acids 67 to 262, of the DHBV core protein were cotransfected into LMH cells along with a replication-deficient construct coding for the DHBV pregenome and polymerase. Neither the N nor the C terminus alone yielded replication-competent core particles. However, cotransfection of plasmids that separately expressed both regions restored a normal replication pattern. Furthermore, the DHBV C terminus but not the N terminus could be replaced by the corresponding domain of the HBV core protein in this assay. Finally, coexpression of the complete HBV core protein and the N terminus from DHBV resulted in DHBV replication, while the HBV core protein alone was not functional. Taken together, these findings suggest a modular organization of the DHBV core protein in which the C terminus is functionally conserved among different hepadnaviruses.
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PMID:Identification of two separable modules in the duck hepatitis B virus core protein. 788 28

Two daughters born to an HBeAg-positive carrier became hepatitis B virus carriers despite immunoprophylaxis with hepatitis B immune globulin or hepatitis B vaccine. The elder daughter received hepatitis B immune globulin alone and the younger daughter received both hepatitis B immune globulin and hepatitis B vaccine. They acquired anti-HBs passively immediately after birth, and the younger daughter did not respond to active immunization. The nucleotide sequence of the S gene of hepatitis B virus DNA from the four carriers in the family was determined. A 531-bp fragment within the S gene, which includes a region encoding both the common a and type-specific d/y or r/w determinants, was amplified by polymerase chain reaction and sequenced. Antigenic subtypes of HBV were identified as adr in the father and adw in both the mother and two daughters. Amino acid residues 122-160 of HBsAg were identical between the daughters and their mother except for a glycine-to-arginine substitution at codon 145. A possibility that this escape mutant had selective advantage over wild-type hepatitis B virus under immune pressure is discussed.
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PMID:Glycine-to-arginine substitution at codon 145 of HBsAg in two infants born to hepatitis B e antigen-positive carrier. 789 45

In a survey of hepatitis B virus (HBV) subtypes using one set of monoclonal typing antibodies, 96.6% of the samples were ad or ay and 3.3% (31) were untypeable. Using two additional antibody panels, 23 samples were ay and ad. Six samples required a third panel to be typed as ay. One sample was not typeable. These last 7 samples were nonreactive or had low reactivity with some antibodies to the common a determinant. Sequencing the HBsAg gene of these 7 samples revealed that amino acid (aa) 122 was arginine, as expected for the y determinant. However, mutations giving rise to serine at aa 120, leucine at aa 143, and glutamic acid at aa 144 were found singly or in combination and correlated with the monoclonal antibody binding patterns. These results have implications for further subtyping surveys, vaccines, immunotherapy, and the design of diagnostic assays, and they give clues to the structure of the major neutralizing epitope of HBV.
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PMID:Molecular characterization of envelope antigenic variants of hepatitis B virus from Spain. 796 32

Phosphorylation of core particles derived either from hepatitis B viruses or from livers of hepatitis B-infected individuals has been long recognized, but the nature and function of the phosphorylating enzyme remained unknown. By immunoblotting with a monoclonal antibody, we have now detected protein kinase C within the liver-derived core particles. To study the significance of the encapsidated protein kinase C for the viral life cycle, we established an in vitro assembly system consisting of Escherichia coli-expressed core protein, protein kinase C, and in vitro-synthesized hepatitis B virus RNA. Phosphorylation of the core protein led to a reduced RNA encapsidation capacity of the core particles. Furthermore, RNA and protein kinase C competed for their target sequence, which is the carboxy-terminal arginine-rich domain of the core protein. This finding implies that phosphorylation of the nucleic acid binding site in the core protein occurs within the particles after encapsidation of protein kinase C, pregenomic RNA, and viral polymerase at a later step during viral genome maturation.
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PMID:Effect of core protein phosphorylation by protein kinase C on encapsidation of RNA within core particles of hepatitis B virus. 796 89


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