Phosphoprotein Crh-Ser46-P Displays Altered Binding to CcpA to Effect Carbon Catabolite Regulation
Journal of Biological Chemistry
In Gram-positive bacteria, the catabolite control protein A (CcpA) functions as the master transcriptional regulator of carbon catabolite repression/regulation (CCR). To effect CCR, CcpA binds a phosphoprotein, either HPr-Ser 46 -P or Crh-Ser 46 -P. Although Crh and histidine-containing protein (HPr) are structurally homologous, CcpA binds Crh-Ser 46 -P more weakly than HPr-Ser 46 -P. Moreover, Crh can form domain-swapped dimers, which have been hypothesized to be functionally relevant in CCR.
... y relevant in CCR. To understand the molecular mechanism of Crh-Ser 46 -P regulation of CCR, we determined the structure of a CcpA-(Crh-Ser 46 -P)-DNA complex. The structure reveals that Crh-Ser 46 -P does not bind CcpA as a dimer but rather interacts with CcpA as a monomer in a manner similar to that of HPr-Ser 46 -P. The reduced affinity of Crh-Ser 46 -P for CcpA as compared with that of HPr-Ser 46 P is explained by weaker Crh-Ser 46 -P interactions in its contact region I to CcpA, which causes this region to shift away from CcpA. Nonetheless, the interface between CcpA and helix ␣2 of the second contact region (contact region II) of Crh-Ser 46 -P is maintained. This latter finding demonstrates that this contact region is necessary and sufficient to throw the allosteric switch to activate cre binding by CcpA. * This work was supported in part by a Burroughs Wellcome Career Development Award 992863 (to M. A. S.) and the Deutsche Forschungsgemeinschaft through SFB 473 and the Fonds der Chemischen Industrie (to W. H.). The Advanced Light Source is supported by the Director, Office under contract DE-AC03-78SF00098 at the Lawrence Berkeley National Laboratory. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The atomic coordinates and structure factors (code 1ZVV for CcpA-(Crh-Ser 46 -P)-cre ternary complex) have been deposited in the Protein . 2 The abbreviations used are: CCR, carbon catabolite repression; cre, catabolite responsive element; CcpA, catabolite control protein A; Crh, catabolite responsive HPr; HPr, histidine containing protein; CRI, contact region I; CRII, contact region II; r.m.s., root mean square; HTH, helix turn helix.