The thermal unfolding of the catabolite activator protein (CAP) of Escherichia coli and the complexes it forms with adenosine cyclic 3',5'-phosphate (cAMP) and guanosine cyclic 3',5'-phosphate (cGMP) was studied by high-sensitivity differential scanning calorimetry (DSC). The thermal denaturation of CAP at pH 7.00 gave an irreversible, symmetrical denaturation curve with a single peak. Distinctly different, more complex DSC curves were obtained for the thermal denaturation of the cAMP-protein and cGMP-protein complexes. The DSC data indicate intermolecular cooperation among CAP dimers, with the extent of oligomerization remaining unchanged during unfolding of the protein. The DSC curves for the thermal denaturation of the cAMP-protein complex and cGMP-protein complex have been resolved into three and two components, respectively, according to the model of independent two-state processes. Analysis of the DSC data suggests two and three independent domains for cGMP-protein and cAMP-protein complexes, respectively, with dissociation of mononucleotide occurring in the second component in both cases during protein denaturation. Furthermore, our studies indicate that the presence of either ligand alters the degree of oligomerization of CAP dimers, cAMP having a greater effect than cGMP. Study holds ProTherm entries: 3845 Extra Details: additive : EDTA(0.2 mM), intermolecular cooperation; oligomerization;,three independent domains; protein denaturation
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:23 p.m.
|Number of data points||4|
|Proteins||cAMP-activated global transcriptional regulator CRP ; cAMP-activated global transcriptional regulator CRP|
|Assays/Quantities/Protocols||Experimental Assay: dCp ; Experimental Assay: dHcal ; Experimental Assay: Tm ; Experimental Assay: dHvH|
|Libraries||Mutations for sequence MVLGKPQTDPTLEWFLSHCHIHKYPSKSTLIHQGEKAETLYYIVKGSVAVLIKDEEGKEMILSYLNQGDFIGELGLFEEGQERSAWVRAKTACEVAEISYKKFRQLIQVNPDILMRLSAQMARRLQVTSEKVGNLAFLDVTGRIAQTLLNLAKQPDAMTHPDGMQIKITRQEIGQIVGCSRETVGRILKMLEDQNLISAHGKTIVVYGTR|