The transition state structure for binding between TAZ1 of CBP and the disordered Hif-1? CAD.

ABSTRACT: Intrinsically disordered proteins (IDPs) are common in eukaryotes. However, relatively few experimental studies have addressed the nature of the rate-limiting transition state for the coupled binding and folding reactions involving IDPs. By using site-directed mutagenesis in combination with kinetics measurements we have here characterized the transition state for binding between the globular TAZ1 domain of CREB binding protein and the intrinsically disordered C-terminal activation domain of Hif-1? (Hif-1? CAD). A total of 17 Hif-1? CAD point-mutations were generated and a ?-value binding analysis was carried out. We found that native hydrophobic binding interactions are not formed at the transition state. We also investigated the effect the biologically important Hif-1? CAD Asn-803 hydroxylation has on the binding kinetics, and found that the whole destabilization effect due the hydroxylation is within the dissociation rate constant. Thus, the rate-limiting transition state is "disordered-like", with native hydrophobic binding contacts being formed cooperatively after the rate-limiting barrier, which is clearly shown by linear free energy relationships. The same behavior was observed in a previously characterized TAZ1/IDP interaction, which may suggest common features for the rate-limiting transition state for TAZ1/IDP interactions.

SUBMITTER: Lindstrom I 

PROVIDER: S-EPMC5959852 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature