¹H, ¹³C, and ¹⁵N backbone resonance assignments of zinc-α2-glycoprotein, a lipid-mobilizing protein structurally related to class I HLA molecules

Abstract Zinc-α2-glycoprotein (ZAG) is a soluble, secreted protein that shares a fold with class I major histocompatibility complex (MHC-I) molecules but does not present antigens to T cells. Instead, ZAG leverages its MHC-I-like groove to bind a diverse set of metal ions, lipids, proteins, and nucleic acids to function in lipid mobilization, metabolism, and cellular signaling. The structural basis of ZAG’s ligand interactions in solution remains poorly understood. Here, we report near-complete (94.6%) backbone (¹H N , ¹⁵N, ¹³Cα, ¹³Cβ, ¹³C′) resonance assignments of perdeuterated, uniformly [²H, ¹⁵N, ¹³C]-labeled human ZAG (32 kDa non-glycosylated form), refolded in vitro from E. coli inclusion bodies and assigned using 3D TROSY-based solution-state NMR experiments. The chemical shifts have been deposited in the Biological Magnetic Resonance Data Bank (BMRB ID: 54025). Backbone amide-amide NOEs and secondary structure predicted by TALOS-N agree closely with the previously published ZAG crystal structure. Comparison with the classical MHC-I molecule HLA-A*02:01 reveals that ZAG’s helical domains and β-sheet platform are similarly rigid and well-ordered in solution, even though ZAG lacks a bound peptide and β2-microglobulin and has diverged functionally. The reported resonance assignments provide a foundation for future NMR studies of ZAG’s structure, biomolecular interactions, conformational dynamics, and biochemical function.