2NZU

Structural mechanism for the fine-tuning of CcpA function by the small molecule effectors G6P and FBP

Summary for 2NZU

• Entry DOI: 10.2210/pdb2nzu/pdb
• Related: 1rzr 1sxg 1sxh 1sxi 1zvv 2nzv
• Descriptor: Catabolite control protein, Phosphocarrier protein HPr, 6-O-phosphono-beta-D-glucopyranose, ... (5 entities in total)
• Functional Keywords: ccpa, ccr, hpr-ser46-p, glucose-6-phosphate, adjunct corepressor, laci-galr, transcription
• Biological source: Bacillus megaterium; More
• Cellular location: Cytoplasm (By similarity): O69250
• Total number of polymer chains: 2
• Total formula weight: 41324.03

Authors

Schumacher, M.A.,Hillen, W.,Brennan, R.G. (deposition date: 2006-11-25, release date: 2007-05-01, Last modification date: 2024-10-09)

Primary citation

Schumacher, M.A.,Seidel, G.,Hillen, W.,Brennan, R.G.
Structural Mechanism for the Fine-tuning of CcpA Function by The Small Molecule Effectors Glucose 6-Phosphate and Fructose 1,6-Bisphosphate.
J.Mol.Biol., 368:1042-1050, 2007

PubMed Abstract: In Gram-positive bacteria, carbon catabolite regulation (CCR) is mediated by the carbon catabolite control protein A (CcpA), a member of the LacI-GalR family of transcription regulators. Unlike other LacI-GalR proteins, CcpA is activated to bind DNA by binding the phosphoproteins HPr-Ser46-P or Crh-Ser46-P. However, fine regulation of CCR is accomplished by the small molecule effectors, glucose 6-phosphate (G6P) and fructose 1,6-bisphosphate (FBP), which somehow enhance CcpA-(HPr-Ser46-P) binding to DNA. Unlike the CcpA-(HPr-Ser46-P) complex, DNA binding by CcpA-(Crh-Ser46-P) is not stimulated by G6P or FBP. To understand the fine-tuning mechanism of these effectors, we solved the structures of the CcpA core, DeltaCcpA, which lacks the N-terminal DNA-binding domain, in complex with HPr-Ser46-P and G6P or FBP. G6P and FBP bind in a deep cleft, between the N and C subdomains of CcpA. Neither interacts with HPr-Ser46-P. This suggests that one role of the adjunct corepressors is to buttress the DNA-binding conformation effected by the binding of HPr-Ser46-P to the CcpA dimer N subdomains. However, the structures reveal that an unexpected function of adjunct corepressor binding is to bolster cross interactions between HPr-Ser46-P residue Arg17 and residues Asp69 and Asp99 of the other CcpA subunit. These cross contacts, which are weak or not present in the CcpA-(Crh-Ser46-P) complex, stimulate the CcpA-(HPr-Ser46-P)-DNA interaction specifically. Thus, stabilization of the closed conformation and bolstering of cross contacts between CcpA and its other corepressor, HPr-Ser46-P, provide a molecular explanation for how adjunct corepressors G6P and FBP enhance the interaction between CcpA-(HPr-Ser46-P) and cognate DNA.

PubMed: 17376479
DOI: 10.1016/j.jmb.2007.02.054

Experimental method

X-RAY DIFFRACTION (2.5 Å)