Production of androgenetic zebrafish (Danio rerio)

To help investigate the evolutionary origin of the imprinting (parent-of-origin mono-allelic expression) of paternal genes observed in mammals, we constructed haploid and diploid androgenetic zebrafish (Danio rerio). Haploid androgenotes were produced by fertilizing eggs that had been X-ray irradiated to eliminate the maternal genome. Subsequent inhibition of the first mitotic division of haploid androgenotes by heat shock produced diploid androgenotes. The lack of inheritance of maternal-specific DNA markers (RAPD and SSR) by putative diploid and haploid androgenotes confirmed the androgenetic origin of their genomes. Marker analysis was performed on 18 putative androgenotes (five diploids and 13 haploids) from six families. None of 157 maternal-specific RAPD markers analyzed, some of which were apparently homozygous, were passed on to any of these putative androgenotes. A mean of 7.7 maternal-specific markers were assessed per family. The survival of androgenetic zebrafish suggests that if paternal imprinting occurs in zebrafish, it does not result in essential genes being inactivated when their expression is required for development. Production of haploid androgenotes can be used to determine the meiotic recombination rate in male zebrafish. Androgenesis may also provide useful information about the mechanism of sex determination in zebrafish.

Cyclic AMP-dependent expression of the Escherichia coli serC-aroA operon

The Escherichia coli serC-aroA operon encodes biosynthetic enzymes for unrelated amino acid biosynthetic pathways leading to the synthesis of serine and the aromatic amino acids. A serC-aroA-lac translational fusion was constructed in the vector pMC1403. Synthesis of beta-galactosidase from the serC-aroA-lac fusion was found to be enhanced in the presence of lactose as the sole carbon source. This enhancement was not observed in strains containing a cya or crp mutant. However, the exogenous addition of cAMP greatly increased the beta-galactosidase synthesis in the cya mutant strain. The serC-aroA mRNA content, analyzed by a dot blot assay, also appeared to increase in the serC+ aroA+ cells after the exogenous addition of cAMP. These findings unambiguously indicate that the expression of the serC-aroA operon is positively controlled by cAMP.

Characterization of Escherichia coli thioredoxins with altered active site residues

Escherichia coli thioredoxin is a small disulfide-containing redox protein with the active site sequence Cys-Gly-Pro-Cys-Lys. Mutations were made in this region of the thioredoxin gene and the mutant proteins expressed in E. coli strains lacking thioredoxin. Mutant proteins with a 17-membered or 11-membered disulfide ring were inactive in vivo. However, purified thioredoxin with the active site sequence Cys-Gly-Arg-Pro-Cys-Lys is still able to serve as a substrate for thioredoxin reductase and a reducing agent in the ribonucleotide reductase reaction, although with greatly reduced catalytic efficiency. A smaller disulfide ring, with the active site sequence Cys-Ala-Cys, does not turn over at a sufficient rate to be an effective reducing agent. Strain in the small ring favors the formation of intermolecular disulfide bonds. Alteration of the invariant proline to a serine has little effect on redox activity. The function of this residue may be in maintaining the stability of the active site region rather than participation in redox activity or protein-protein interactions. Mutation of the positively charged lysine in the active site to a glutamate residue raises the Km values with interacting enzymes. Although it has been proposed that the positive residue at position 36 is conserved to maintain the thiolate anion on Cys-32 (Kallis & Holmgren, 1985), the presence of the negative charge at this position does not alter the pH dependence of activity or fluorescence behavior. The lysine is most likely conserved to facilitate thioredoxin-protein interactions.

In vitro construction of gshB::kan in Escherichia coli and use of gshB::kan in mapping the gshB locus

The Escherichia coli structural gene for glutathione synthetase, gshB, was cloned into pBR322. Plasmids containing gshB were able to complement the glutathione requirement of a trxA gshB double mutant, and cells containing the plasmids were found to have elevated levels of glutathione synthetase. A mutant gshB allele was constructed by inserting the kan gene from pUC4K into a unique HpaI site located within gshB. The resulting plasmid-encoded allele was used to replace a genomic gshB+ by homologous recombination. The resulting strain had no detectable glutathione synthetase activity. The gshB allele containing the kan insertion was used to map gshB on the E. coli chromosome by P1 transduction. The results indicated that gshB is located at 63.4 min, between metK and speC. The allele was further localized to a region of 3,100 to 3,120 kilobase pairs on the physical map (restriction map) of E. coli by DNA-DNA hybridization to a series of lambda bacteriophages (Y. Kohara, K. Akiyama, and K. Isono, Cell 50:495-508, 1987).

Characterization of Escherichia coli-Anabaena sp. hybrid thioredoxins

Thioredoxin is a small redox protein with an active-site disulfide/dithiol. The protein from Escherichia coli has been well characterized. The genes encoding thioredoxin in E. coli and in the filamentous cyanobacterium Anabaena PCC 7119 have been cloned and sequenced. Anabaena thioredoxin exhibits 50% amino acid identity with the E. coli protein and interacts with E. coli enzymes. The genes encoding Anabaena and E. coli thioredoxin were fused via a common restriction site in the nucleotide sequence coding for the active site of the proteins to generate hybrid genes, coding for two chimeric thioredoxins. These proteins are designated Anabaena-E. coli (A-E) thioredoxin for the construct with the Anabaena sequence from the N-terminus to the middle of the active site and the E. coli sequence to the C-terminus, and E. coli-Anabaena (E-A) for the opposite construct. The gene encoding the A-E thioredoxin complements all phenotypes of an E. coli thioredoxin-deficient strain, whereas the gene encoding E-A thioredoxin is only partially effective. Purified E-A thioredoxin exhibits a much lower catalytic efficiency with E. coli thioredoxin reductase and ribonucleotide reductase than either E. coli or Anabaena thioredoxin. In contrast, the A-E thioredoxin has a higher catalytic efficiency in these reactions than either parental protein. Reaction with antibodies to E. coli and Anabaena thioredoxins shows that the antigenic determinants for thioredoxin are located in the C-terminal part of the molecule and retain the native conformation in the hybrid proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning, expression, and nucleotide sequence of a gene encoding a second thioredoxin from Corynebacterium nephridii

A gene encoding thioredoxin in Corynebacterium nephridii was cloned in Escherichia coli by complementation of a thioredoxin mutant. Transformants that appeared to complement were analyzed for the presence of thioredoxin by the coupled assay using methionine sulfoxide reductase. Of 18 transformants, four contained high levels of thioredoxin activity. Transformants containing plasmids pLCN2 and pLCN4 were unable to support replication of T7 phage, in spite of their thioredoxin activities, and were studied in more detail. The plasmid pLCN2 contains a 1.85-kilobase Sau3AI insert, whereas pLCN4 contains a 10-kilobase TaqI insert. These plasmids complement all phenotypes of a thioredoxin-deficient strain except for replication of T7 phage. The nucleotide sequence of a 620-base pair HinfI fragment encoding thioredoxin derived from either plasmid indicated that the protein derived from this DNA is different from the thioredoxin of C. nephridii previously reported (Meng, M., and Hogenkamp, H.P.C. (1981) J. Biol. Chem. 256, 9174-9182). The amino acid sequence predicted from the nucleotide sequence shows a high degree of homology with other procaryotic thioredoxins. However, the new thioredoxin contains the tetrapeptide -Cys-Ala-Pro-Cys- at the active site and a third half-cystine residue in the carboxyl-terminal domain of the protein. The molecular weight of this thioredoxin, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is smaller than that estimated from the DNA sequence, suggesting that processing may have occurred.

Cloning, expression, and characterization of the Anabaena thioredoxin gene in Escherichia coli

The gene encoding thioredoxin in Anabaena sp. strain PCC 7119 was cloned in Escherichia coli based on the strategy that similarity between the two thioredoxins would be reflected both in the gene sequence and in functional cross-reactivity. DNA restriction fragments containing the Anabaena thioredoxin gene were identified by heterologous hybridization to the E. coli thioredoxin gene following Southern transfer, ligated with pUC13, and used to transform an E. coli strain lacking functional thioredoxin. Transformants that complemented the trxA mutation in E. coli were identified by increased colony size and confirmed by enzyme assay. Expression of the cloned Anabaena thioredoxin gene in E. coli was substantiated by subsequent purification and characterization of the algal protein from E. coli. The amino acid sequence derived from the DNA sequence of the Anabaena gene was identical to the known amino acid sequence of Anabaena thioredoxin. The E. coli strains which expressed Anabaena thioredoxin complemented the TrxA- phenotype in every respect except that they did not support bacteriophage T7 growth and had somewhat decreased ability to support bacteriophages M13 and f1.

Prognostic evaluation of endoscopic sclerotherapy on bleeding esophageal varices

From November 1981 to March 1984, 100 patients with esophageal varices bleeding were treated by endoscopic sclerotherapy.

The combined peri and intravasal method was applied, using Äthoxysclerol as a sclerosant.

The 79 cases were followed after sclerotherapy over a period ranging from 3 months to 26 months.

The amount of transfused blood on presclerotherapy was 4–5 pints and in 2/3 cases 1–2 pints were needed on postsclerotherapy.

Seven cases (8.1 per cent) had complications; 2 cases developed esophageal stenosis, 3 cases aspiration pneumonia, and 2 cases mediastinitis.

Fortunately, all 7 cases recovered. Rebleeding occurred in 15 cases (19.0 per cent); namely 3 cases (3.8 per cent) within 6 months, 5 cases (6.3 per cent) in the period from 6 months to 12 months and 7 cases (8.9 per cent) after 12 months.

During the follow up period, 14 cases died. Their causes of death were as follows: 6 cases died of hepatic failure, 5 cases died of hepatoma, and 3 cases expired from uncontrollable bleeding.

Based on data, it appears to be possible to control the bleeding in 97 per cent of the esophageal varices bleeding on their (first) bleeding.

Cloning and nucleotide sequence of the trxA gene of Escherichia coli K-12

The Escherichia coli K-12 trxA gene, the gene encoding thioredoxin, has been cloned and sequenced. The DNA sequence includes 280 base pairs upstream and 46 base pairs downstream of the coding region. The downstream sequence contains the -35 region of the promoter of the rho gene. Northern analysis of the trxA mRNA and S1 nuclease mapping indicate the presence of two promoters for the trxA gene. Initiation from either promoter results in an mRNA containing two potential translation initiation codons, one of which could initiate synthesis of a protein 18 amino acids longer than the mature trxA gene product. The 3' end of the gene, including the last eight codons, contains a stable stem-loop structure (delta G = -12.9 kcal) typical of a rho-independent transcription termination signal.

Thioredoxin is the bacterial protein encoded by fip that is required for filamentous bacteriophage f1 assembly

Escherichia coli mutants defective in the fip gene contain reduced levels of thioredoxin activity. F' derivatives of trxA mutants failed to support f1 growth, although suppressors of an amber trxA mutation restored both thioredoxin activity and the Fip+ phenotype. Plasmids carrying the trxA gene restored the Fip+ phenotype to fip strains.