title: Characterization of the organic component of low-molecular-weight chromium-binding substance and its binding of chromium.
abstract: Chromium was proposed to be an essential element over 50 y ago and was shown to have therapeutic potential in treating the symptoms of type 2 diabetes; however, its mechanism of action at a molecular level is unknown. One chromium-binding biomolecule, low-molecular weight chromium-binding substance (LMWCr or chromodulin), has been found to be biologically active in in vitro assays and proposed as a potential candidate for the in vivo biologically active form of chromium. Characterization of the organic component of LMWCr has proven difficult. Treating bovine LMWCr with trifluoroacetic acid followed by purification on a graphite powder micro-column generates a heptapeptide fragment of LMWCr. The peptide sequence of the fragment was analyzed by MS and tandem MS (MS/MS and MS/MS/MS) using collision-induced dissociation and post-source decay. Two candidate sequences, pEEEEGDD and pEEEGEDD (where pE is pyroglutamate), were identified from the MS/MS experiments; additional tandem MS suggests the sequence is pEEEEGDD. The N-terminal glutamate residues explain the inability to sequence LMWCr by the Edman method. Langmuir isotherms and Hill plots were used to analyze the binding constants of chromic ions to synthetic peptides similar in composition to apoLMWCr. The sequence pEEEEGDD was found to bind 4 chromic ions per peptide with nearly identical cooperativity and binding constants to those of apoLMWCr. This work should lead to further studies elucidating or eliminating a potential role for LMWCr in treating the symptoms of type 2 diabetes and other conditions resulting from improper carbohydrate and lipid metabolism.
authors: Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA.
authors: Yuan
authors: Y
authors: Chen
authors: Heather M
authors: HM
authors: Watson
authors: Junjie
authors: J
authors: Gao
authors: Sarmistha Halder
authors: SH
authors: Sinha
authors: Carolyn J
authors: CJ
authors: Cassady
authors: John B
authors: JB
authors: Vincent
references: J Nutr. 1994 Jan;124(1):117-9
references: 8283288
references: Arch Biochem Biophys. 1997 Mar 15;339(2):335-43
references: 9056266
references: Physiol Genomics. 2006 Nov 27;27(3):370-9
references: 16940432
references: Rapid Commun Mass Spectrom. 1999 Jun;13(12):1175-1185
references: 10407294
references: Biochem Biophys Res Commun. 1989 Aug 30;163(1):189-93
references: 2775259
references: Toxicol Appl Pharmacol. 1981 Jul;59(3):515-23
references: 7268774
references: J Am Chem Soc. 2003 Jan 22;125(3):774-80
references: 12526678
references: Comp Biochem Physiol B Biochem Mol Biol. 2006 Aug;144(4):423-31
references: 16815060
references: J Nutr. 2000 Apr;130(4):715-8
references: 10736319
references: Tohoku J Exp Med. 1987 Jul;152(3):211-9
references: 3310334
references: Rapid Commun Mass Spectrom. 2005;19(23):3607-11
references: 16276489
references: J Biol Inorg Chem. 2011 Mar;16(3):381-90
references: 21086001
references: Anal Chem. 2006 Nov 15;78(22):7861-9
references: 17105181
references: Biochemistry. 1997 Apr 15;36(15):4382-5
references: 9109644
references: J Inorg Biochem. 1984 Oct;22(2):91-102
references: 6502162
references: Reprod Toxicol. 2002 May-Jun;16(3):223-36
references: 12128095
references: J Nutr. 1988 Jan;118(1):39-45
references: 3275760
references: Dalton Trans. 2010 Apr 28;39(16):3787-94
references: 20372701
references: Proteomics. 2002 Sep;2(9):1277-87
references: 12362346
references: Biomed Mass Spectrom. 1984 Nov;11(11):601
references: 6525415
references: Biochemistry. 1996 Oct 1;35(39):12963-9
references: 8841143
references: Ind Health. 1983;21(1):35-41
references: 6841148
references: J Biol Inorg Chem. 2000 Feb;5(1):129-36
references: 10766445
references: Eur J Biochem. 1987 Jun 15;165(3):627-31
references: 3595604
references: Sangyo Igaku. 1981 Sep;23(5):505-12
references: 7328856
references: Biophys J. 1984 Oct;46(4):541-3
references: 6498270
references: J Mass Spectrom. 2008 Jun;43(6):773-81
references: 18205239
references: BMC Chem Biol. 2004 Dec 16;4(1):2
references: 15603587