Part:BBa_K200011

The temperature sensitive lamda cI repressor protein has a cI857 mutation that results in denaturation of the repressor when the temperature is raised from 30 to 42°C, thereby allowing lambda promoter expression. cI1</cite)

The repressor normally negatively regulates the expression of genes from the bacteriophage lambda pL and pR promoters. This repressive action is strongest at 30°C. <cite>cI2</cite)

However, when the temperature is raised, typically to 42°C, the functionality of the protein is lost and the cI repressor is no longer able to bind to the operators on its promoter. Therefore, lambda promoter expression increases.