Properties and cellular functions of related yeast ER proteins protein disulphide-isomerase and Eug1p.
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Biomedical subjects
Publications and source records attributed to D Pioli.
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We have found an influence of cellular ubiquitin levels over the secretion of human leucocyte elastase inhibitor (elafin) by Saccharomyces cerevisiae. Inactivation of the UBI4 polyubiquitin gene reduced elafin secretion 3 to 4-fold. Conversely ubiquitin overexpression, by galactose induction of an integrated UBI4 gene under GAL1 promoter control, enhanced elafin secretion 7-fold compared to cells wild-type for ubiquitin genes. This influence of ubiquitin levels is exerted at a post-transcriptional step in elafin gene expression, and may represent a chaperone-like action. Ubiquitin overexpression did not affect production of alpha-factor and of certain natural yeast extracellular enzymes even though appreciable free ubiquitin became associated with the yeast periplasm.
The renin-encoding genes have been cloned from high (Ren-1d, Ren-2d)- and low (Ren-1c)-renin-producing strains of mice (DBA/2J and C57BL/10). Each of the genes is approx. 9.6 kb in length and consists of nine exons and eight introns. The entire nucleotide sequence of the Ren-1d gene has been determined and the 5'-flanking regions of the three genes, Ren-1c, Ren-1d and Ren-2d, have been compared. The significance of several potential regulatory signals found in the DNA is discussed.
Replacement of the solvent-exposed residues of the DNA recognition helix of the 434 repressor with the corresponding residues of the P22 repressor generates a hybrid protein, 434R[alpha 3(P22R)], which binds specifically to P22 operators. We show here that a new DNA-binding specificity is generated by combining 434 and 434R[alpha 3(P22R)] repressor monomers to form a heterodimer. The heterodimer specifically recognizes a chimeric P22/434 operator that lacks two-fold rotational symmetry.
Cells of Escherichia coli containing a chemically synthesized human alpha 1 interferon (IFN-alpha 1) gene, under control of the lac promoter, make a product with biological properties indistinguishable from those of the natural IFN-alpha 1 [antiviral activity, acid stability, species crossreactivity, inactivation by antisera directed against leukocyte or Namalwa cell interferon, and stimulation of (2'-5')oligoadenylate synthetase activity]. Similar levels of IFN synthesis were obtained when the expression unit (lac promoter plus synthetic IFN-alpha 1 gene) was transplanted into the obligate methylotroph Methylophilus methylotrophus.
The glutamate dehydrogenase gene of Escherichia coli has been cloned into broad host-range plasmids and can complement glutamate synthase mutants of Methylophilus methylotrophus. Assimilation of ammonia via glutamate dehydrogenase is more energy-efficient than via glutamate synthase, thus the recombinant organism converts more growth substrate, methanol, into cellular carbon.
Pseudomonas aeruginosa PA01 was found to utilise both the D- and L-isomers of alpha-alanine and also beta-alanine as sole sources of carbon and energy for growth. Enzymological studies of wild-type cultures and comparison with mutants deficient in growth upon one or more isomers of alanine led to the following conclusions: (i) utilisation of D-alanine involved its direct oxidation by an inducible, membrane-bound, cytochrome-linked dehydrogenase; (ii) utilisation of L-alanine required its conversion to the directly oxidisable D-form by a soluble racemase; (iii) utilisation of beta-alanine, like L-alanine, involves both the racemase and D-alanine dehydrogenase enzymes, but in addition must involve other enzymes the identity of which is still speculative; (iv) P. aeruginosa, like Escherichia coli, appears to take up D-alanine and L-alanine by means of two specific permeases.