Structure of full-length transcription regulator CcpA in the apo form.

The catabolite control protein A (CcpA) from Bacillus megaterium is a member of the bacterial repressor protein family GalR-LacI. CcpA functions as master transcriptional regulator of carbon catabolite repression/regulation in firmicutes. Here we present the crystal structure of full-length apo CcpA at 2.5 A resolution from B. megaterium. The structure reveals the location of the helix-turn-helix domain as well as the hinge region, which were not visible due to their high flexibility in earlier crystallographic studies on CcpA molecules. The structure of the apo CcpA homodimer in the present form is in contrast to other reported structures for CcpA.