Thermodynamics, structure, and antibacterial activity of the decavanadate-lysozyme complex

Area of Science:

• Biochemistry and Biophysics
• Protein-Polyanion Interactions
• Materials Science

Background:

• Highly charged polyanions can significantly alter protein structure and function.
• Understanding these interactions is crucial for developing novel biomaterials and therapeutics.
• The lysozyme-decavanadate system serves as a model for protein-polyanion complexation.

Purpose of the Study:

• To investigate the thermodynamic, structural, and functional effects of decavanadate binding to lysozyme.
• To characterize the formation and stability of the lysozyme-decavanadate complex.
• To evaluate the antibacterial activity of the complex.

Main Methods:

• Integrated experimental techniques: Isothermal titration calorimetry (ITC), fluorescence spectroscopy (SF), electrospray ionization mass spectrometry (ESI-MS), circular dichroism (CD) spectroscopy.
• Computational approach: Molecular dynamics (MD) simulations.
• Biological assays to assess antibacterial activity against various bacterial strains.

Main Results:

• Formation of a 2:1 decavanadate:lysozyme complex at pH 5.0, primarily stabilized by electrostatic interactions.
• MD simulations identified the C-terminal region as the primary binding site.
• CD spectroscopy revealed significant α-helical structure reduction in lysozyme upon binding, yet catalytic activity remained unaffected.
• The complex exhibited enhanced antibacterial efficacy against Gram-positive bacteria (B. subtilis, S. aureus) compared to Gram-negative strains (E. coli, P. aeruginosa).

Conclusions:

• Decavanadate binding induces conformational changes in lysozyme without compromising its enzymatic function.
• The lysozyme-decavanadate complex demonstrates potent, synergistic antibacterial properties.
• This study highlights the potential of protein-polyanion complexes as antimicrobial agents.