Archives of Biochemistry and Biophysics | VOL. 729
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Different phenotypic outcome due to site-specific phosphorylation in the cancer-associated NQO1 enzyme studied by phosphomimetic mutations

Publication Date Oct 1, 2022

Abstract

Protein phosphorylation is a common phenomenon in human flavoproteins although the functional consequences of this site-specific modification are largely unknown. Here, we evaluated the effects of site-specific phosphorylation (using phosphomimetic mutations at sites S40, S82 and T128) on multiple functional aspects as well as in the structural stability of the antioxidant and disease-associated human flavoprotein NQO1 using biophysical and biochemical methods. In vitro biophysical studies revealed effects of phosphorylation at different sites such as decreased binding affinity for FAD and structural stability of its binding site (S82), conformational stability (S40 and S82) and reduced catalytic efficiency and functional cooperativity (T128). Local stability measurements by H/D exchange in different ligation states provided structural insight into these effects. Transfection of eukaryotic cells showed that phosphorylation at sites S40 and S82 may reduce steady-levels of NQO1 protein by enhanced proteasome-induced degradation. We show that site-specific phosphorylation of human NQO1 may cause pleiotropic and counterintuitive effects on this multifunctional protein with potential implications for its relationships with human disease. Our approach allows to establish relationships between site-specific phosphorylation, functional and structural stability effects in vitro and inside cells paving the way for more detailed analyses of phosphorylation at the flavoproteome scale.

Concepts

Site-specific Phosphorylation Phosphomimetic Mutations Human Flavoprotein Human NQO1 Counterintuitive Effects Functional Cooperativity Multifunctional Protein Biochemical Methods Conformational Stability Protein Phosphorylation

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No potential conflict of interest was reported by the authors. The conception and design of the study, acquisition of data, analysis and interpretatio...

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