ISSN:
0749-503X
Keywords:
Cytochrome P450 14DM
;
recombinant DNA
;
plasmid copy number
;
regulated gene expression
;
galactose induction
;
mRNA and protein levels
;
chemostat cultivation
;
Life and Medical Sciences
;
Genetics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
The Saccharomyces cerevisiae Lanosterol 14α-demethylase (14DM) gene was overxpressed in S. cerevisiae using Promoter sequences of the highly expressed S. cerevisiae glyceraldehyde-3-phosphate dehydrogenase TDH3 gene. To investigate factors affecting 14DM overproduction, the levels of 14DM-specific specific RNAs, apoprotein, and heme protein, repectively, were determined and the 14DM-specific RNA levels compared with the RNA levels originating from the enodogenous TDH gene(s). The quantitative measurements revealed that the 14DM steady-state RNA levels reached were some three-to five-fold below the theoretically expected values. With a View towards futrher improving expression of the 14DM gene, the specing between the TDH3 promoter and the AUG was adjusted precisely and to rule out possible toxic effects exerted by the 14DM protein, the TDH3 promoter was placed under galactose regulation by introducing an UASG segment. Furthermore, the effects of the gene copy number on 14DM overproduction were investigated. From the analysis of the improved expression constructs five conclusions could be reached: (1) experssion from the native 14DM gene is comparable to the expression driven by the TDH3 promoter-14DM fusion construct on single copy plasmid vectors; (2) expression from the TDH3 promoter-14DM construct on single-copy vectors is nearly as effcient as expression from the corresponding endogenous TDH3 gene; (3) the gene copy number has an effect on the relative expression levels of the TDH3 promoter-14DM constructs; (4) the steady-state amounts of protein produced are very nearly proportional to gene dosage; and (5) protein toxicity does not have a major impact on 14DM production. The maximum yield of 14DM was in the order of 7% of the total yeast protein and the maximum production of functional 14DM heme protein appears to be limited by the availability of heme.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/yea.320080704
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