Protein‐Protein Stabilization in V^IVO/8‐Hydroxyquinoline–Lysozyme Adducts

Abstract

The binding of the potential drug [VIVO(8‐HQ)2], where 8‐HQ is 8‐hydroxyquinolinato, with hen egg white lysozyme (HEWL) was evaluated through spectroscopic (electron paramagnetic resonance, EPR, and UV‐visible), spectrometric (electrospray ionization‐mass spectrometry, ESI‐MS), crystallographic (X‐ray diffraction, XRD), and computational (DFT and docking) studies. ESI‐MS indicates the interaction of [VIVO(8‐HQ)(H2O)]+ and [VIVO(8‐HQ)2(H2O)] species with HEWL. Room temperature EPR spectra suggest both covalent and non‐covalent binding of the two different V‐containing fragments. XRD analyses confirm these findings, showing that [VIVO(8‐HQ)(H2O)]+ interacts covalently with the solvent exposed Asp119, while cis‐[VIVO(8‐HQ)2(H2O)] non‐covalently with Arg128 and Lys96 from a symmetry mate. The covalent binding of [VIVO(8‐HQ)(H2O)]+ to Asp119 is favored by a π–π contact with Trp62 and a H‐bond with Asn103 of a symmetry‐related molecule. Additionally, the covalent binding of VVO2+ to Asp48 and non‐covalent binding of other V‐containing fragments to Arg5, Cys6, and Glu7 is revealed. Molecular docking indicates that, in the absence of the interactions occurring at the protein‐protein interface close to Asp119, the binding to Glu35 or Asp52 should be preferred. Such a protein‐protein stabilization could be more common than what believed up today, at least in the solid state, and should be considered in the characterization of metal–protein adducts.