Abstract
The interaction between the C-terminal transactivation domain of HIF-1α (CTAD-HIF-1α) and the transcriptional adapter zinc binding 1 (TAZ1) domain of CREB binding protein participate in the initiation of gene transcription during hypoxia. Unbound CTAD-HIF-1α is disordered but undergoes a disorder-to-order transition upon binding to TAZ1. We have here performed NMR side chain and backbone relaxation studies on TAZ1 and side chain relaxation measurements on CTAD-HIF-1α in order to investigate the role of picosecond to nanosecond dynamics. We find that the internal motions are significantly affected upon binding, both on the side chain and the backbone level. The dynamic response corresponds to a conformational entropy change that contributes substantially to the binding thermodynamics for both binding partners. Furthermore, the conformational entropy change for the well-folded TAZ1 varies upon binding to different IDP targets. We further identify a cluster consisting of side chains in bound TAZ1 and CTAD-HIF-1α that experience extensive dynamics and are part of the binding region that involves the N-terminal end of the LPQL motif in CTAD-HIF-1α; a feature that might have an important role in the termination of the hypoxic response.
Highlights
Molecular recognition by proteins is an essential part of many cellular processes
To what extent does the side chain and backbone dynamics of the folded protein change when interacting with different intrinsically disordered protein (IDP), and what does this mean in terms of energetic contribution to the overall binding thermodynamics? What is the dynamic character of the bound IDP? there is a need to perform studies that addresses the internal motions for both binding partners
This demonstrates that transcriptional adapter zinc binding 1 (TAZ1), a well-folded protein domain, can have a backbone dynamic response that varies depending on the binding partner
Summary
Molecular recognition by proteins is an essential part of many cellular processes. While we have, during the last decades, greatly advanced our understanding on the molecular details of protein-ligand interactions, in particular the structural basis for such interactions, the significant role conformational entropy can have in molecular recognition is more recent[1,2,3,4] and not as well understood. In this study, investigated the role of picosecond to nanosecond (ps-ns) dynamics in the interaction between the folded transcriptional adapter zinc binding 1 (TAZ1) domain of CREB binding protein (CBP)[14,15] and the C-terminal transactivation domain of hypoxia inducible factor subunit 1α (CTAD-HIF-1α)[16,17] by NMR. Many of the previously published NMR ps-ns dynamics studies on protein binding have mostly focused on backbone motions, but it has been demonstrated that it is crucial to investigate side chain dynamics, which can correspond to substantial conformational entropy, are heterogeneous, are involved in allosteric phenomena, and can have a significant response upon binding[1,4,6,11,26,27]. The analysis of side chain dynamics reveals the presence of a cluster consisting of side chains from both TAZ1 and CTAD-HIF-1α that are highly dynamic and are part of a certain binding region that is important in the competition for TAZ1 binding between CTAD-HIF-1α and the CITED2 protein
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