title: Dissecting allosteric effects of activator-coactivator complexes using a covalent small molecule ligand.
abstract: Allosteric binding events play a critical role in the formation and stability of transcriptional activator-coactivator complexes, perhaps in part due to the often intrinsically disordered nature of one or more of the constituent partners. The kinase-inducible domain interacting (KIX) domain of the master coactivator CREB binding protein/p300 is a conformationally dynamic domain that complexes with transcriptional activators at two discrete binding sites in allosteric communication. The complexation of KIX with the transcriptional activation domain of mixed-lineage leukemia protein leads to an enhancement of binding by the activation domain of CREB (phosphorylated kinase-inducible domain of CREB) to the second site. A transient kinetic analysis of the ternary complex formation aided by small molecule ligands that induce positive or negative cooperative binding reveals that positive cooperativity is largely governed by stabilization of the bound complex as indicated by a decrease in koff. Thus, this suggests the increased binding affinity for the second ligand is not due to an allosteric creation of a more favorable binding interface by the first ligand. This is consistent with data from us and from others indicating that the on rates of conformationally dynamic proteins approach the limits of diffusion. In contrast, negative cooperativity is manifested by alterations in both kon and koff, suggesting stabilization of the binary complex.
authors: Program in Chemical Biology,Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109.
authors: Ningkun
authors: N
authors: Wang
authors: Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109Departments of Chemistry and.
authors: Jean M
authors: JM
authors: Lodge
authors: Program in Chemical Biology,Departments of Chemistry andBiological Chemistry, amapp@umich.edu fierke@umich.edu.
authors: Carol A
authors: CA
authors: Fierke
authors: Program in Chemical Biology,Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109Departments of Chemistry and amapp@umich.edu fierke@umich.edu.
authors: Anna K
authors: AK
authors: Mapp
mesh_terms: D000494:Allosteric Regulation; D008024:Ligands; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D050880:p300-CBP Transcription Factors / Q000737:chemistry*
chemical_list: D008024:Ligands; D050880:p300-CBP Transcription Factors
keywords: IDP; protein–protein interaction