Biomedical subjects

J A Erratt

Publications and source records attributed to J A Erratt.

5 recordsLinked to original sources

PubMed1986

Allelism within the DEX and STA gene families in Saccharomyces diastaticus.

Saccharomyces diastaticus produces an extracellular glucoamylase and is therefore capable of hydrolyzing and fermenting starch. Tamaki (1978) studied starch utilization in S. diastaticus and found three polymeric genes controlling this function: STA1, STA2 and STA3. Independently, Erratt and Stewart (1978) studied dextrin utilization by the yeast S. diastaticus and designated the gene, which they identified, DEX1. Erratt and Stewart (1981 a, b) later described two other genes which controlled glucoamylase production in S. diastaticus: DEX2 and a third which was allelic to STA3. At that time STA1 and STA2 were not available to test for allelism in the DEX gene family. In this study strains containing the remaining 4 genes have been examined to determine if further allelism exists between the two gene families. It was ascertained that DEX1 is allelic to STA2 and DEX2 is allelic to STA1. Therefore, no new gene controlling starch utilization has been identified and these two nomenclatures can now be consolidated into one. Based on the fact that the glucoamylase from S. diastaticus can hydrolyze both dextrin and starch, dextrin being the term used to describe partially hydrolyzed starch, and the more wide use of the nomenclature STA, we propose to retain STA as the designation for genes coding for glucoamylase production in S. diastaticus.

Alleles↗

PubMed1986

Cloning and expression of a Saccharomyces diastaticus glucoamylase gene in Saccharomyces cerevisiae and Schizosaccharomyces pombe.

A recombinant plasmid pool of the Saccharomyces diastaticus genome was constructed in plasmid YEp13 and used to transform a strain of Saccharomyces cerevisiae. Six transformants were obtained which expressed amylolytic activity. The plasmids each contained a 3.9-kilobase (kb) BamHI fragment, and all of these fragments were cloned in the same orientations and had identical restriction maps, which differed from the map of the STA1 gene (I. Yamashita and S. Fukui, Agric. Biol. Chem. 47:2689-2692, 1983). The glucoamylase activity exhibited by all S. cerevisiae transformants was approximately 100 times less than that of the donor strain. An even lower level of activity was obtained when the recombinant plasmid was introduced into Schizosaccharomyces pombe. No expression was observed in Escherichia coli. The 3.9-kb BamHI fragment hybridized to two sequences (4.4 and 3.9 kb) in BamHI-digested S. diastaticus DNA, regardless of which DEX (STA) gene S. diastaticus contained, and one sequence (3.9 kb) in BamHI-digested S. cerevisiae DNA. Tetrad analysis of crosses involving untransformed S. cerevisiae and S. diastaticus indicated that the 4.4-kb homologous sequence cosegregated with the glucoamylase activity, whereas the 3.9-kb fragment was present in each of the meiotic products. Poly(A)+ RNA fractions from vegetative and sporulating diploid cultures of S. cerevisiae and S. diastaticus were probed with the 3.9-kb BamHI fragment. Two RNA species, measuring 2.1 and 1.5 kb, were found in both the vegetative and sporulating cultures of S. diastaticus, whereas one 1.5-kb species was present only in the RNA from sporulating cultures of S. cerevisiae.

Cloning, Molecular↗

PubMed1985

Replicating instabilities in yeast: occurrence in different mutational systems.

Following mutagenesis of yeast cells with nitrosoguanidine, primary mosaic colonies exhibiting prototrophic/auxotrophic phenotypes were obtained. Upon replating of these primary mosaics, numerous secondary mosaics were present in the progeny. This study shows that replicating instabilities occur at many different loci within the Schizosaccharomyces pombe genome. In addition, the ade-1 gene of Saccharomyces cerevisiae (causing red pigmentation) was used to show that the phenomenon also occurs in this yeast.

Ascomycota↗

PubMed1985

Glucanase gene diversity in prokaryotic and eukaryotic organisms.

A number of bacteria and eukaryotes produce extracellular enzymes that degrade various types of polysaccharides including the glucans starch, cellulose and hemicellulose (xylan). The similarities in the modes of expression and specificity of enzyme classes, such as amylase, cellulose and xylanase, suggest common genetic origins for particular activities. Our determination of the extent of similarity between these glucanases suggests that such data may be of very limited use in describing the early evolution of these proteins. The great diversity of these proteins does allow identification of their most highly conserved (and presumably functionally important) regions.

Amino Acid Sequence↗

PubMed1984

The induction of alpha-amylase by starch in Aspergillus oryzae: evidence for controlled mRNA expression.

The induction of alpha-amylase by starch has been studied in the filamentous fungus Aspergillus oryzae. Low levels of alpha-amylase activity were found in both intracellular and extracellular samples from glucose-grown cultures. However, alpha-amylase activity increased when starch was the sole carbon source. The intracellular enzyme activity was induced by a factor of approximately 6.5, while the extracellular activity increased 20-fold over that found in the glucose-grown cultures. Regardless of the carbon source or cellular location, the molecular weight of the active protein was 52 500 +/- 1800 and only this protein reacted with antibodies specific for alpha-amylase. A parallel study of the in vitro translated proteins directed by poly(A)+ RNA fractions indicated a presumptive alpha-amylase with a similar isoelectric point but with a molecular weight of approximately 54 000. This protein was most prevalent using RNA from early, exponentially growing cultures in starch medium. Immunoprecipitation data indicate that the abundance of alpha-amylase transcripts decreases dramatically after the first 12 h, reflecting an initial transcription control for the expression of this enzyme.

Animals↗