A proposed mechanism for how Mediator regulates the amplitude (strength) of transcription is based on different conformational states. These, in turn, provide different degrees of efficiency for the re-entry of RNA pol II into PIC during re-initiation. According to this hypothetical model, what is postulated to determine the conformational shape of the Mediator?

In thos case, different conformational states may trigger the activation of the protein function. Generally, these conformational states are the result of posttranslational modifications such as, for example, protein phosphorylation  

Explanation:

In eukaryotes, the mediator complex acts to regulate the transcriptional activity. This complex interacts with the RNA polymerase II and  transcriptional factors in order to activate transcription

a. the production of carbon dioxide through the process of photosynthesis