Galactose induction

Leuther, K. K., and S. A. Johnston, Nondissociation of GAL4 and GAL80 in vivo after Galactose Induction. Science 256 1333-1336, 1992. 

Microbial Expression of the 14-1 cDNA Encoded Polyphenolic Protein. Following transformation of a haploid yeast strain with the YpGX285 expression vector, initial studies were performed at the shake-flask level to determine whether polyphenolic protein was produced by the yeast cells upon galactose induction. Those studies demonstrated that the cells were producing the polyphenolic protein derivative and that the product was homogeneous and of the expected molecular weight. 

Ginsenan S-IIA, a polysaccharide fraction from the roots of P. ginseng is a potent inducer of IL-8 production by human monocytes and THP-1 cells, and this induction is accompanied by increased IL-8 mRNA expression. The polysaccharide appears from the structural feature to be a mixture of arabino-galactan type I and type II, based on the presence of 1,3-, 1,6-, 1,3,6-, 1,4-, and 1,4,6-galactose units as well as terminal arabinose and 1,5-, 1,3,5-, and 1,2,5-linked units. It also contains 1,4,6-linked glucose units that together with the 1,2,5-linked arabinose units are different from the units found in other ginseng polysaccharides and may thus be of importance for the activity [64]. 

Galactose oxidase of P. circinatus was apparently inhibited by traces of BESOD. It can be inactivated by H Oj produced in the reaction unless catalase was added. There was an activation by traces of O J. In the absence of oxidants the reaction usually showed an induction period The enzyme, used at very low concentrations in the assays, was protected by proteins like serumalbumin. SOD did, however, not alter the reaction rate when added after 15 min This was interpreted by an inactivation of SOD by the H O accumulated in the reaction but it could just as well mean that SOD had no effect on the active enzyme, but that it did lower the activation in the induction period. Peroxidase activated galactose oxidase and suppressed the effect of SOD It did protect the enzyme against H O inactivation and could have been responsible for appreciable amounts of OJ, produced from O and from radicals formed in its action on a substrate. 

In the induction of enzymes of galactose metabolism in E. coli, three enzymes are involved -galactosidase (which catalyses the hydrolysis of the y -glycosidic bonds of lactose), galactose permease (which is responsible for transport of lactose across the cell membrane) and a third enzyme, A-protein, apparently not directly involved in galactose metabolism. The system has an environmental inducer, galactose, and in its presence the number of /)-galactosidase molecules rises from 5-10 to 10,000 within the cell. The addition of the inducer can increase the protein production in less than five minutes after its addition. Protein synthesis of these enzymes stops almost immediately in the absence of lactose. 

Yeast Genetics. The yeast strain used in these studies was YGXD8 (MAT a /ew2-3 leu2-112). Yeast cells were transformed by the spheroplast method of Hinnen et al. (21). The transformed cells were maintained in YNB medium (0.7% yeast nitrogen base) supplemented with 5% glucose. For induction of polyphenolic protein synthesis, the cells were cultured in YP medium (1% yeast extract, 1% bacto-peptone) supplemented with 4% glucose and 2% galactose. 

D-galactose-grown yeast de Robichon-Szulmajster (1958) kinase under control of gene GAL1 Adams (1972) 4 kinase induction and repression... 

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