Process of Protein Production
So, let's talk about how protein production works. As I have said in my previous post, protein production starts when mercury ions bind to the MerR. Also, when the cells have to express proteins, they tend to undergo a lot of stress. When doing research, we cannot risk exposure to mercury ions every time we need a sample for analysis. In other words, we will not risk our lives, to that extent, in the name of science when there are other alternatives around. So, instead of mercury ions present, we use a generic molecule which induces production of all proteins in a cell continuously till stopped by the researchers. This generic molecule is Isopropyl β-D-1-thiogalactopyranoside, abbreviated IPTG.
IPTG binds very tightly to MerR (or any other protein regulator). Usually, any kind of generic inducer is degraded by the cell to prevent over-expression of proteins and relieve the cells from a lot of stress. So, the IPTG binds tightly to the receptor in a way that prevents the cell from degrading it and stopping the production of proteins.
The above image is a cartoon representation of what is happening in the cell for a different protein, but the only thing different is that GFP is one block, and in our cells we could have that block for the production of MerT, MerF, MerP, MerR, MerD, MerA, or MerB. The green arrows mean that the expresion of protein starts from there. LacI, which is present in almost all cells, is the natural repressor to prevent the cell from going into over-expression of proteins and stress. This repressor comes off when there is abundance of inducing molecules that bind to it, for e.g., excess mercury ions or IPTG. The IPTG then binds to LacI and the expression of protein starts from then till the inducer molecules are not present or the researcher stops the cells from growing.
In the next blog post, I will talk about what kind of cells are used to produce these proteins and possibly how their DNA is modified in the lab.