Team:Stockholm/Modelling/Suitable model

With the mentioned details, first step should be about preparing a proper model for allolactose/lactose dynamics. The reason to this is the binding of allolactose to LacI and inhibiting it from binding to operator, which will result in gene expression. [http://www.ncbi.nlm.nih.gov/pubmed/12719218 Yildirim N et al 2002] proposed a mathematical model for lac operon induction in E. Coli. The details that they considered in the model are what we are looking for: external lactose, internal lactose, conversion of lactose to allolactose and glucose, interaction of allolactose with LacI (Lac Repressor) and mRNA. Since on the plasmid that we are using to express our genes in bacteria, LacI also acts as repressor, it is reasonable to use the same model as [http://www.ncbi.nlm.nih.gov/pubmed/12719218 Yildirim N et al 2002].

We start slowly by talking a little about Lac operon in E. Coli. Lac operon is responsible for transport and metabolism of lactose in e coli. It has a promoter site and three structural genes (LacZ, LacY and LacA). Availability of external Lactose and Glucose regulates this operon. In the absence of Lactose the LacI gene - which is always expressed, codes for the repressor and represses the expression the of Lac operon. When Lactose is available again for the bacteria in the absence of glucose, Allolactose (a β-galactosidase side reaction) binds to repressor and makes it impossible for the repressor to bind the operator on Lac operon. This will result in production of high levels of LacZ (β-galactosidase) , LacY (β-galactoside permease) and LacA; the latter is not interesting for our case. Lacz and LacY expression will lead to more production of Allolactose(a metabolite of lactose).