A novel binuclear Pd(ii) complex displaying synergic peptide cleavage behaviour.

Area of Science:

• Coordination Chemistry
• Biochemistry
• Proteomics

Background:

• Mononuclear palladium(II) complexes are known artificial proteases, cleaving peptides at histidine, cysteine, and methionine residues.
• Exploring novel palladium(II) complexes could lead to advanced tools for 'Omics' studies, enhancing protein analysis.

Purpose of the Study:

• To construct and investigate the peptide hydrolysis activity of a novel binuclear palladium(II) complex, [Pd2(μ-O-L-H)(μ-Cl)](ClO4)2.
• To elucidate the cleavage mechanism and specificity of this binuclear complex compared to mononuclear analogues.

Main Methods:

• Synthesis of the binuclear palladium(II) complex.
• Electrophoresis and liquid chromatography-tandem mass spectrometry (LC-MS-MS) for peptide cleavage analysis.
• Theoretical studies to understand the complex's interaction with peptides and proteins.

Main Results:

• The binuclear palladium(II) complex demonstrated selective myoglobin cleavage at the second upstream peptide bond from histidine and methionine.
• Histidine- and methionine-orientated hydrolysis were confirmed, but cysteine-orientated hydrolysis was not observed.
• Cysteine residues inhibited histidine-orientated hydrolysis, while oxidized cysteine restored it, suggesting a unique interaction mechanism.

Conclusions:

• The binuclear palladium(II) complex exhibits distinct peptide cleavage behavior, primarily targeting histidine and methionine residues.
• A synergistic mechanism involving two palladium(II) centers is proposed for hydrolysis, with cysteine forming a bridging structure that inhibits cleavage.
• This study introduces a polynuclear strategy for fine-tuning the peptide cleavage specificity of palladium(II) complexes, offering potential in biochemical research.