Sigma protein

The core RNA polymerase consists of enzymes which are capable of carrying out the transcription of RNA from DNA. It is the co-ordinated activities of enzymes of RNA Polymerase that result in the transcription. However, none of these enzymes are able to locate the starting point. It is the sigma protein which by recognizing thepromoter sequence points out and hence direct the RNA Polymerase to the starting point of gene.