Non-enzymatic phosphorylation of bovine serum albumin by Cr(V) complexes: Role in Cr(VI)-induced phosphorylation and toxicity

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• 作者：Chellappa Vasant ; Sundararaj Sankaramanivel ; Mahadevan Jana ; Rama Rajaram and Thirumalachari Ramasami
• 关键词：Cr(V) complexes ; Cr(VI) ; non ; enzymatic phosphorylation ; reactive oxygen species ; Src ; family kinases ; apoptosis ; chromium toxicity
• 刊名：Molecular and Cellular Biochemistry
• 出版年：2005
• 出版时间：July 2005
• 年：2005
• 卷：275
• 期：1-2
• 页码：153-164
• 全文大小：493 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Biochemistry
  Medical Biochemistry
  Oncology
  Cardiology
  
• 出版者：Springer Netherlands
• ISSN：1573-4919

文摘

Evidence for the non-enzymatic phosphorylation of bovine serum albumin (BSA) by sodium bis(2-ethyl-2-hydroxybutyrato)oxochromate(V), Na[CrVO(ehba)₂], 1, sodium bis(2-hydroxy-2-methylbutyrato)oxochromate(V), Na[CrVO(hmba)₂], 2 and potassium dichromate, K₂Cr₂O₇, 3 in the presence of labeled adenosine-5′-triphosphate (ATP) under conditions of physiological pH is presented. Aggregation and extent of phosphorylation of BSA mediated by 1, 2 or 3 seems to increase with the concentration and time of incubation of the reaction mixture containing all the reactants. The [γ-32P] label in ATP is incorporated into aggregates of BSA in the in vitro reaction of the protein with ATP in the presence of 1, 2 or 3. Phosphorylation of BSA by ATP in the absence of 1, 2 or 3 is negligible. Addition of EDTA reverses aggregation of protein and liberates partially the incorporated phosphate label. The stoichiometry of phosphorylation is found to be the highest and is equal to 12.25 mol PO₄3−/mol BSA in the presence of 500 μM of 1, which decreases to 10.56 mol PO₄3−/mol BSA after EDTA treatment. Resistance to the removal of phosphate label by EDTA increases with increase in time of incubation. Dialysis of phosphorylated BSA reverses the incorporated [γ-32P] label only partially, indicating the formation of covalent links of phosphate groups to BSA. Evidence for the site of phosphorylation in the reaction mediated by 1, 2 or 3 being hydroxyl side groups of tyrosine and serine/threonine residues has been gained. Based on the results, a possibility that 1, 2 and 3 mimic the function of tyrosine and serine/threonine kinases has been invoked.