Construction of a regulated PGK expression vector.
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Biomedical subjects
Publications and source records attributed to E Hinchliffe.
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We report the cloning of the Aspergillus niger glucose oxidase gene and its use to elevate glucose oxidase productivity in A. niger by increasing the gene dosage. In addition, the gene has been introduced into A. nidulans where it provides the novel capacity to produce glucose oxidase. A plasmid, in which DNA encoding the mature form of glucose oxidase was preceded by a Saccharomyces cerevisiae secretion signal, effected high-level production of extracellular glucose oxidase in this yeast.
We have constructed a set of hybrid yeast Escherichia coli vectors which utilise the site specific recombination function of the Saccharomyces cerevisiae 2 microns plasmid to completely eliminate the bacterial moiety upon introduction into yeast. A number of these plasmids have been shown to exhibit high inheritable stability in both laboratory and industrial strains during non-selective growth. These plasmids are beneficial for the genetic modification of industrial yeast, particularly those used in the production of food and beverages, and are of benefit in the study of plasmid maintenance and heterologous gene expression.
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EcoRI fragments of DNA from Bacillus subtilis NCIB 8565, a high producer of an endo-1,3-1,4-beta-D-glucanase, were 'shot-gun' cloned in the plasmid vector pBR325. A 3.5 kb insert, carrying single restriction sites for AvaI, BglII, ClaI, PvuI and PvuII, was shown to direct the synthesis of beta-glucanase in Escherichia coli K12. Enzyme activity was demonstrated in extracellular fractions of E. coli harbouring the beta-glucanase gene; however, the largest proportion (greater than 50%) of total enzyme activity was periplasmic in location. beta-Glucanase activity and cellular location were independent of the orientation of the 3.5 kb fragment in pBR325.
The par region of pSC101, required in cis to promote its stable inheritance, was joined, in combination with the tetr determinant of pBR325, to large and small minichromosomes. These hybrid minichromosomes were examined for stability and found to be no more stable than their parent minichromosomes. Indeed, one recombinant plasmid, pEH21, showed reduced stability, which was not attributable to a reduced copy number. Neither pEH21 nor pEH22, a plasmid composed of the same DNA arranged differently, was stabilized by the presence of a Par+ pSC101 derived replicon in the same cell. We conclude that the par region of pSC101 does not stabilize minichromosomes.
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A naturally occurring transmissible plasmid, designated pAV1, has been isolated in Acinetobacter calcoaceticus. It specifies resistance to sulphonamides and is capable of mobilizing two non-transmissible resistance determinants for tetracycline and neomycin, respectively, within strains of A. calcoaceticus. It is incompatible with the P class R factors RP4 and R751 in A. calcoaceticus. On this basis we conclude that pAV1 is a member of the P incompatibility group. However, unlike most other P group R factors, pAV1 is not transmissible to strains of Escherichia coli, Pseudomonas aeruginosa, Klebsiella or Proteus mirabilis.
The naturally occurring transmissible plasmid pAV1 mediates chromosome transfer and can exhibit two distinct levels of transmissibility in Acinetobacter calcoaceticus strain EBF65/65. The two states of pAV1 have been arbitrarily designated pAV1a (low frequency variant) and pAV1b (high frequency variant). Both variants have the same incompatibility and host range properties and each mobilizes two non-transmissible resistance determinants for tetracycline and neomycin. Sex factor activity has been shown to be stable: however, pAV1b fertility variants can be derived from pAV1a donors following conjugal transfer of pAV1 into new recipient strains of EBF65/65.
Acinetobacter calcoaceticus strain EBF65/65 harbours a cryptic plasmid, pAV2, which has been shown by electrophoretic separation on agarose gels to have a molecular mass of approximately 13.5 megadaltons (Md). Transfer of the previously described sex factor pAV1 (Hinchliffe & Vivian, 1980 a,b) from the hospital strainJC17 into strains possessing pAV2 occurs only at a low frequency, whereas transfer to similar strains lacking pAV2 occurs at a much higher frequency. In EBF65/65, pAV1 may be present in strains possessing or lacking pAV2; pAV1 strains lacking pAV2 correspond to strains previously described as pAV1a (Hinchliffe & Vivian, 1980b) whereas pAV1 strains which also possess pAV2 correspond to pAB1b strains. The genetic evidence presented here is consistent with the hypothesis that pAV2 specifies a host restriction and modification system that is active against pAV1. Physical evidence from agarose gel electrophoresis indicates that pAV1 corresponds to a band of approximately 85 Md in strain JC17. The corresponding band in strains of EBF65/65 is difficult to distinguish because of the presence of a further cryptic plasmid band of approximately 88 Md, designated pAV3. A small cryptic plasmid of approximately 6 Md, designated pAV4, is reported for EBF65/65.
The naturally occurring plasmid pAV2 restricts the entry of the P class plasmid RP4 and the W class plasmids R388 and S-a into Acinetobacter calcoaceticus strain EBF65/65 from Escherichia coli. The W class plasmids only transfer from E. coli into pAV2-strains. Plasmid RP4 is modified in the presence of pAV2 such that it is no longer restricted on entry into pAV2 recipients of strain EBF65/65.