NDLI: Evaluation of the binding of oxovanadium(IV) to human serum albumin

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Cobbinna, Enoch Correia, Isabel Tomaz, Isabel Jakusch, Tamás Pessoa, João Costa Mehtab, Sameena Rockenbauer, Antal Nagy, Nóra V. Kiss, Tamás
Description	Author Affiliation: Correia I ( Centro de Química Estrutural, Instituto Superior Técnico, Lisbon, Portugal.)
Abstract	The understanding of the biotransformations of insulin mimetic vanadium complexes in human blood and its transport to target cells is an essential issue in the development of more effective drugs . We present the study of the interaction of oxovanadium(IV) with human serum albumin (HSA) by electron paramagnetic resonance ( EPR ), circular dichroism (CD) and visible absorption spectroscopy . Metal competition studies were done using $Cu^{II}$ and $Zn^{II}$ as metal probes. The results show that $V^{IV}O$ occupies two types of binding sites in albumin, which compete not only with each other, but also with hydrolysis of the metal ion. In one of the sites the resulting $V^{IV}O–HSA$ complex has a weak visible CD signal and its X-band EPR spectrum may be easily measured. This was assigned to amino acid side chains of the ATCUN site. The other binding site shows stronger signals in the CD in the visible range, but has a hardly measurable EPR signal; it is assigned to the multi metal binding site (MBS) of HSA. Studies with fatted and defatted albumin show the complexity of the system since conformational changes, induced by the binding of fatty acids , decrease the ability of $V^{IV}O$ to bind albumin. The possibility and importance of ternary complex formation between $V^{IV}O,$ HSA and several drug candidates – maltol (mal), picolinic acid (pic), 2-hydroxypyridine- N-oxide (hpno) and 1,2-dimethyl-3-hydroxy-4(1 H)-pyridinone (dhp) was also evaluated. In the presence of maltol the CD and EPR spectra significantly change, indicating the formation of ternary VO–HSA– maltol complexes. Modeling studies with amino acids and peptides were used to propose binding modes. Based on quantitative RT EPR measurements and CD data, it was concluded that in the systems with mal, pic, hpno, and dhp $(V^{IV}OL_{2})_{n}(HSA)$ species form, where the maximum value for n is at least 6 (mal, pic). The degree of formation of the ternary species, corresponding to the reaction $V^{IV}OL_{2}$ + HSA ⇆ $V^{IV}OL_{2}(HSA)$ is hpno > pic ≥ mal > dhp. $(V^{IV}OL)_{n}(HSA)$ type complexes are detected exclusively with pic. Based on the spectroscopic studies we propose that in the $(V^{IV}OL_{2})_{n}(HSA)$ species the protein bounds to vanadium through the histidine side chains.
ISSN	14779226
Issue Number	21
Volume Number	41
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2012-06-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Biomimetic Materials Metabolism Serum Albumin Vanadates Binding, Competitive Circular Dichroism Copper Electron Spin Resonance Spectroscopy Humans Protein Binding Temperature Zinc Journal Article Research Support, Non-U.S. Gov't Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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