2oen
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| , resolution 3.17Å | |||||||
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| Ligands: | |||||||
| Gene: | ccpA (Bacillus megaterium), ptsH (Bacillus megaterium) | ||||||
| Related: | 2NZU, 2NZV
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| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Structural mechanism for the fine-tuning of CcpA function by the small molecule effectors glucose-6-phosphate and fructose-1,6-bisphosphate
OverviewOverview
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.
About this StructureAbout this Structure
2OEN is a Protein complex structure of sequences from Bacillus megaterium. Full crystallographic information is available from OCA.
ReferenceReference
Structural mechanism for the fine-tuning of CcpA function by the small molecule effectors glucose 6-phosphate and fructose 1,6-bisphosphate., Schumacher MA, Seidel G, Hillen W, Brennan RG, J Mol Biol. 2007 May 11;368(4):1042-50. Epub 2007 Feb 27. PMID:17376479
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