Structure of the Na,K-ATPase regulatory protein FXYD2b in micelles: Implications for membrane–water interfacial arginines

•The structure of FXYD2b is determined in micelles by NMR.•Several arginines yield orientation-dependent solid-state NMR signals.•Arginine side chains may hydrogen bond with lipid head groups.•The FXYD motif adopts a helical fold.•Additional FXYD-containing sequences are identified.

FXYD2 is a membrane protein responsible for regulating the function of the Na,K-ATPase in mammalian kidney epithelial cells. Here we report the structure of FXYD2b, one of two splice variants of the protein, determined by NMR spectroscopy in detergent micelles. Solid-state NMR characterization of the protein embedded in phospholipid bilayers indicates that several arginine side chains may be involved in hydrogen bond interactions with the phospholipid polar head groups. The structure and the NMR data suggest that FXYD2b could regulate the Na,K-ATPase by modulating the effective membrane surface electrostatics near the ion binding sites of the pump. This article is part of a Special Issue entitled: NMR Spectroscopy for Atomistic Views of Biomembranes and Cell Surfaces. Guest Editors: Lynette Cegelski and David P. Weliky.

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