During our project we had a great deal of work with different types of promoters - constitutive and indusible. During the planning of the project and the accumulation of knowledge about the various parts, we discovered that much information is lacking about many of these parameters, and the information that exists exists scattered among many places and is not arranged in one place. We chose two modulators - TDH3 [https://parts.igem.org/Part:BBa_K124002] of team iGEM08_Brown and PGK1 [https://parts.igem.org/Part:BBa_K2110012]of team iGEM16_Tianjin, two strong constitutive permutative promoters, and improved their descriptions and information about them, referring to the main sources we used. We hope that groups coming after us will have faster and more convenient access to information when they come to choose the parameters they want to use.
Improve an existing part
We chose to take the existing BBA part of miraculin, and improve it by adding the HXT7 promoter we have already isolated.
Our new part is HXT7_miraculin - BBa_K2408024 https://parts.igem.org/wiki/index.php?title=Part:BBa_K2408024
HXT7 transcription was repressed at high glucose levels and was detected when the glucose in the culture approached depletion.
All hexose transporter proteins Hxt2, 4, 6 and 7 in S. cerevisiae are repressed by high glucose concentration, and induced when glucose concentration decreases below a certain level.
HXT7 seems to bind glucose with the highest affinity among all glucose transporters, and this fact is associated to a strong induction at low glucose level. The HXT7 promoter region turned out to be suitable for recombinant protein production in yeast and was compared to other yeast promoters (PTEF1, PADH1, PTPI1, PPGK1, PTDH3 and PPYK1) using lacZ as a reporter gene. Among them, PHXT7 was stated as the strongest promoter in continuous culture with limited glucose level.
https://microbialcellfactories.biomedcentral.com/articles/10.1186/1475-2859-13-5#CR44
http://onlinelibrary.wiley.com/doi/10.1002/yea.771/pdf
Since transcription of genes with the HXT7 promoter was correlated with the extracellular glucose concentration in the cultures, we can cause the miraculin to be released only when the glucose levels are low and thus adjust the level of its secretion to the desired taste in wine - at a high concentration of glucose it will not be dispensed, and at low concentration it will be secreted and improve the wine's sweet taste.