PMID:20226195
| Citation |
Sarraf, NS, Baardsnes, J, Cheng, J, O'Connor-McCourt, M, Cygler, M and Ekiel, I (2010) Structural basis of the regulation of the CbpA co-chaperone by its specific modulator CbpM. J. Mol. Biol. 398:111-21 |
|---|---|
| Abstract |
CbpA, one of the Escherichia coli DnaJ homologues, acts as a co-chaperone in the DnaK chaperone system. Despite its extensive similarity in domain structure and function to DnaJ, CbpA has a unique and specific regulatory mechanism mediated through the small protein CbpM. Both CbpA and CbpM are highly conserved in bacteria. Earlier studies showed that CbpM interacts with the N-terminal J-domain of CbpA inhibiting its co-chaperone activity but the structural basis of this interaction is not known. Here, we have combined NMR spectroscopy, site-directed mutagenesis and surface plasmon resonance to characterize the CbpA/CbpM interaction at the molecular level. We have determined the solution structure of the CbpA J-domain and mapped the residues that are perturbed upon CbpM binding. The NMR data defined a broad region on helices alpha2 and alpha 3 as involved in the interactions. Site-directed mutagenesis has been used to further delineate the CbpA J-domain/CbpM interface. We show that the binding sites of CbpM and DnaK on CbpA J-domain overlap, which suggests a competition between DnaK and CbpM for binding to CbpA as a mechanism for CbpA regulation. This study also provides the explanation for the specificity of CbpM for CbpA versus DnaJ, by identifying the key residues for differential binding. |
| Links |
PubMed Online version:10.1016/j.jmb.2010.03.006 |
| Keywords |
Amino Acid Substitution; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Binding Sites; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Escherichia coli Proteins/physiology; Gene Expression Regulation, Bacterial; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Chaperones/genetics; Molecular Chaperones/metabolism; Mutagenesis, Site-Directed; Plasmids/genetics; Protein Structure, Secondary/genetics; Protein Structure, Tertiary/genetics; Surface Plasmon Resonance |
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