Central glycolytic gene regulator (CGGR) protein, molecular model. This protein binds to DNA (deoxyribonucleic acid) in the absence of glucose, blocking the transcription of certain genes, specifically the gapA operon. An operon is a cluster of genes under the control of a single regulatory signal. This regulator protein is from the bacterium Bacillus subtilis, affecting the production of enzymes for triose phosphate interconversion reactions. The structure is two protein chains (green and pink).