Multiple and Variable Binding of Pharmacologically Active Bis(maltolato)oxidovanadium(IV) to Lysozyme

Abstract

The interaction with proteins of metal-based drugs plays a crucial role in their transport, mechanism, and activity. For an active ML n complex, where L is the organic carrier, various binding modes (covalent and non-covalent, single or multiple) may occur and several metal moieties (M, ML, ML 2 , etc.) may interact with proteins. In this study, we have evaluated the interaction of [V IV O(malt) 2 ] (bis(maltolato)oxidovanadium(IV) or BMOV, where malt = maltolato, i.e., the common name for 3-hydroxy-2methyl-4H-pyran-4-onato) with the model protein hen egg white lysozyme (HEWL) by electrospray ionization mass spectrometry, electron paramagnetic resonance, and X-ray crystallography. The multiple binding of different V-containing isomers and enantiomers to different sites of HEWL is observed. The data indicate both noncovalent binding of cis-[VO(malt) 2 (H 2 O)] and [VO(malt)-(H 2 O) 3 ] + and covalent binding of [VO(H 2 O) 3−4 ] 2+ and cis-[VO(malt) 2 ] and other V-containing fragments to the side chains of Glu35, Asp48, Asn65, Asp87, and Asp119 and to the C-terminal carboxylate. Our results suggest that the multiple and variable interactions of potential V IV OL 2 drugs with proteins can help to better understand their solution chemistry and contribute to define the molecular basis of the mechanism of action of these intriguing molecules.

Implications of Protein Interaction in the Speciation of Potential VIVO–Pyridinone Drugs

“…The absence of other signals in the region 3960–4100 G suggests that the formation of adducts with a covalent bond between the [V IV O­(empp) 2 ] moiety and a side chain of HEWL, in principle possible in the axial accessible site of 1a or in the equatorial site of 1b , does not occur. This is in contrast with what was observed when HEWL reacts with cis -[V IV O­(malt) 2 ], where the formation of a V IV –O­(Asn) bond has been demonstrated with XRD . The larger steric hindrance and/or lower stabilization through secondary interactions such as hydrogen bonds or van der Waals contacts for [V IV O­(empp) 2 ] may account for these experimental findings.…”

“…The comparison with [V IV O­(empp) 2 ]/HEWL allows one to find differences and similarities of the two systems, described graphically in Figure . While cis -[V IV O­(malt) 2 (H 2 O)] gives both noncovalent and covalent binding through the replacement of the water molecule by Asn65 side chain, in the structures here obtained, only the noncovalent interaction of cis -[V IV O­(empp) 2 (H 2 O)] is observed. In the [V IV O­(malt) 2 ]/HEWL system, covalent or noncovalent interaction of various isomerswith two equatorial phenolato-O – or two equatorial keto-Ois found; moreover, three enantiomers ( OC -6–24-Λ, OC -6–24-Δ, and OC -6–34-Δ) are present in the adducts . In contrast, with empp(−) only the isomer with two equatorial phenolato-O – and only the enantiomer OC -6–24-Λ binds to HEWL. The interaction with [V IV O­(empp) 2 ] is favored in the two systems with pH 7.0 and 7.5 (structures B and C ), when this species reaches its maximum amount as suggested by the concentration distribution curves in Figure . Despite the 1:1 V-empp species should not exist at pH 7.0, the adduct HEWL–[V IV O­(empp)­(H 2 O)] + is detected in solution with ESI-MS and EPR, and both [V IV O­(empp)­(H 2 O)] + and [V IV O­(empp)­(H 2 O) 2 ] + are revealed with XRD in the solid state adducts.…”

“…It is covalent at pH 4.5 and noncovalent at pH 7.0. In the [V IV O­(malt) 2 ]/HEWL system, instead, only a noncovalent interaction of [V IV O­(malt)­(H 2 O) 3 ] + was ascertained The oxidation of V IV to V V with formation of the trinuclear species [V V 3 O 6 (empp) 3 (H 2 O)] is observed in the [V IV O­(empp) 2 ]/HEWL system.…”

“…The interaction of proteins with VCs can be covalent or noncovalent. Regarding the first type of binding, the interaction depends on the thermodynamic stability and chemical form of the specific VC: up to four donors could bind V IV O 2+ ion, two donors the fragment V IV OL + , and one donor the equatorial or axial site of cis -octahedral or square pyramidal V IV OL 2 species, respectively. , Until now, structural determinations of the adducts formed by V IV O–L moieties with proteins through X-ray diffraction (XRD) are still scarce. − In the system with [V IV O­(malt) 2 ], hen egg white lysozyme (HEWL) interacts both noncovalently and covalently with the moieties V IV O 2+ and V IV O­(malt) + , generated upon hydrolysis, and with cis -[V IV O­(malt) 2 (H 2 O)] and cis -[V IV O­(malt) 2 ] fragments, the binding occurring with only one donor of the side chain of Glu35, Asp48, Asn65, and Asp87 residues . In contrast, with V IV O­(H 2 O)­(bipy/phen) the binding of HEWL takes place with the simultaneous coordination of Asn46 and Asp52 .…”

Complexities of the interaction of Ni(II), Pd(II) and Pt(II) pyrrole-imine chelates with human serum albumin

“…[47] Metallodrug candidates are no exception and recent work has shown how half-sandwich Ru II and Rh III complexes bind to HSA as intact species through coordination to His and Glu residues with retention of the arene. [52][53][54] Generally, protein binding by metal complexes is accompanied by ligand dissociation [55][56][57][58] while non-dissociative binding is less common, [59][60][61][62] often though not exclusively [63] hinging on multidentate ligands that provide kinetic inertness and thermodynamic stability. [64,65] Here, we synthesized a popular tetradentate bis(pyrroleimine) ligand, H2PrPyrr, and its isoelectronic (nd 8 ) square-planar chelates of Ni II , Pd II , and Pt II , denoted M(PrPyrr) (Figure 1a).…”