Isolation of a novel chromium(III) binding protein from bovine liver tissue after chromium(VI) exposure

Abstract

In the ongoing investigation into the biological importance and toxicity issues surrounding the bioinorganic chemistry of chromium, the accepted literature procedure for the isolation of the biological form of chromium, low molecular weight chromium binding protein (LMWCr) or chromodulin, was investigated for its specificity. When chromium(VI) is added to bovine liver homogenate, results presented here indicate at least four chromium(III) binding peptides and proteins are produced and that the process is non-specific for the isolation of LMWCr. A novel trivalent chromium containing protein (1) has been isolated to purity and initial characterization is reported here. Chromium(III) identification was determined by optical spectroscopy and diphenylcarbazide testing. This chromium binding protein has a molecular weight of 15.6 kDa, which was determined from both gel-electrophoresis and mass spectrometry. The protein is comprised primarily of Asx, Glx, His, Gly/Thr, Ala, and Lys in a 1.00:2.51:0.37:2.09:0.39:1.17 ratio and is anionic at pH 7.4. In addition, the protein binds approximately 2.5 chromium(III) ions per molecule.

The role of Chromium III in the organism and its possible use in diabetes and obesity treatment

“…However, the experiments with Cr supplementation can be also interpreted as a result of non-specific binding of Cr to the amino acid sequences. These types of proteins were found in rat liver (9 proteins with a molecular weight from 4 -97 kDa) and bovine liver (15.6 kDa) [18,55]. Furthermore, chromodulin activity stimulating the insulin receptor tyrosine kinase is unspecific.…”

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

“…Before each analysis, the column was flushed with 100 µL of the mobile phase spiked with 10 mM EDTA. The chromatographic effluent was directly introduced via PEEK tubing into the HPLC UVvisible detector for evaluation of protein absorbance at 570 nm, corresponding to Cr(III) d-d transitions (Döker et al, 2010;Peterson et al, 2008), and subsequently delivered to the ICP-MS for 52 Cr analysis. Molecular masses of Cr-binding biomolecules from the HSP fractions were estimated using the molecular weight calibration curve (0.1 -10 kDa), even for the metal-ligand complexes that eluted outside the linear mass separation range reported for the SECpep column.…”

Safety and efficacy of chromium methionine (Availa® Cr) as feed additive for all species

“…The finding of nine different types of high molecular weight Cr-containing proteins in rat liver, with masses ranging from 4 to 97 kDa (Feng et al, 2003), also supports the view of rather nonspecific bindings of Cr(III) by proteins. Recently, a novel Cr(III) binding protein (15.6 kDa) was isolated from bovine liver tissue after Cr(VI) exposure, further suggesting on non-specific process of Cr(III) binding by proteins (Peterson et al, 2008). In addition, the effect of chromodulin lacks the experimental evidence of specificity in stimulating tyrosine kinase activity.…”