title: Protection of aquo/hydroxocobalamin from reduced glutathione by a B12 trafficking chaperone.
abstract: We identified a bovine B(12) trafficking chaperone bCblC in Bos taurus that showed 88% amino acid sequence identity with a human homologue. The protein bCblC was purified from E. coli by over-expression of the encoding gene. bCblC bound cyanocobalamin (CNCbl), methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl) in the base-off states and eliminated the upper axial ligands forming aquo/hydroxocobalamin (OH(2)/OHCbl) under aerobic conditions. A transition of OH(2)/OHCbl was induced upon binding to bCblC. Interestingly, bCblC-bound OH(2)/OHCbl did not react with reduced glutathione (GSH), while the reaction of free OH(2)/OHCbl with GSH resulted in the formation of glutathionylcobalamin (GSCbl) and glutathione disulfide (GSSG). Furthermore we found that bCblC eliminates the GSH ligand of GSCbl forming OH(2)/ OHCbl. The results demonstrated that bCblC is a B(12) trafficking chaperone that binds cobalamins and protects OH(2)/OHCbl from GSH, which could be oxidized to GSSG by free OH(2)/OHCbl.
authors.affiliation: School of Biotechnology, Yeungnam University, Gyeongsan, Korea.
authors.forename: Jinju
authors.initials: J
authors.lastname: Jeong
authors.forename: Tal Soo
authors.initials: TS
authors.lastname: Ha
authors.forename: Jihoe
authors.initials: J
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D005978:Glutathione / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006879:Hydroxocobalamin / Q000737:chemistry / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D014805:Vitamin B 12 / Q000737:chemistry / Q000378:metabolism*; D014803:Vitamin B Complex / Q000378:metabolism
chemical_list: D018832:Molecular Chaperones; D014803:Vitamin B Complex; D005978:Glutathione; D014805:Vitamin B 12; D006879:Hydroxocobalamin