Conformational exchange of the Z alpha domain of human RNA editing enzyme ADAR1 studied by NMR spectroscopy

Abstract

Z-DNA binding proteins (ZBPs) play important roles in RNA editing, innate immune responses, and viral infections. Numerous studies have implicated a role for conformational motions during ZBPs binding upon DNA, but the quantitative intrinsic conformational exchanges of ZBP have not been elucidated. To understand the correlation between the biological function and dynamic feature of the Z alpha domains of human ADAR1 (hZ alpha(ADAR1)), we have performed the N-15 backbone amide Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments on the free hZ alpha(ADAR1) at two different magnetic fields at 35 degrees C. The robust inter-dependence of parameters in the global fitting process using multi-magnetic field CPMG profiles allows us characterizing the dynamic properties of conformational changes in hZ alpha(ADAR1). This study found that free hZ alpha(ADAR1) exhibited the conformational exchange with a k(ex) of 5784 s(-1) between the states "A" (89% population) and "B" (11% population). The different hydrophobic interactions among helices alpha 1, alpha 2, and alpha 3 between these two states might correlate with efficient Z-DNA binding achieved by the hydrogen bonding interactions between its side-chains and the phosphate backbone of Z-DNA. (C) 2021 Elsevier Inc. All rights reserved.