Title
Unveiling the folding mechanism of the Bromodomains
Author
Maria Petrosino, Daniela Bonetti, Alessandra Pasquo, Laura Lori, Roberta Chiaraluce, Valerio Consalvi, Carlo Travaglini-Allocatelli
Year
2017
Journal
Biochemistry and Biophysics Reports
Abstract
Bromodomains (BRDs) are small protein domains often present in large multidomain proteins involved in transcriptional regulation in eukaryotic cells. They currently represent valuable targets for the development of inhibitors of aberrant transcriptional processes in a variety of human diseases. Here we report urea-induced equilibrium unfolding experiments monitored by circular dichroism (CD) and fluorescence on two structurally similar BRDs: BRD2(2) and BRD4(1), showing that BRD4(1) is more stable than BRD2(2). Moreover, we report a description of their kinetic folding mechanism, as obtained by careful analysis of stopped-flow and temperature-jump data. The presence of a high energy intermediate for both proteins, suggested by the non-linear dependence of the folding rate on denaturant concentration in the millisec time regime, has been experimentally observed by temperature-jump experiments. Quantitative global analysis of all the rate constants obtained over a wide range of urea concentrations, allowed us to propose a common, three-state, folding mechanism for these two BRDs. Interestingly, the intermediate of BRD4(1) appears to be more stable and structurally native-like than that populated by BRD2(2). Our results underscore the role played by structural topology and sequence in determining and tuning the folding mechanism.
Instrument
J-720
Keywords
Circular dichroism, Secondary structure, Protein folding, Protein denaturation, Thermodynamics, Biochemistry