title: Oxygen-dependent oxidation of Fe(II) to Fe(III) and interaction of Fe(III) with bovine serum albumin, leading to a hysteretic effect on the fluorescence of bovine serum albumin.
abstract: The serum albumin is the most abundant protein in blood plasma and the iron is essential for many cellular processes. However, the interaction between Fe(3+) and haem-free serum albumin remains unclear. Here we provide evidence for the fact that haem-free BSA possesses one specific Fe(3+)-binding site. The binding of Fe(3+) to BSA results in a significant quenching of the Trp fluorescence of BSA. The average apparent dissociation constant value for the interaction of Fe(3+) and BSA is 3.46 x 10(-8)+/-3 x 10(-10) M at 37 degrees C and 3.30 x 10(-8)+/-5 x 10(-10) M at 25 degrees C, respectively, as determined by fluorescence titration. Addition of 50 microM Fe(2+) to 1 microM BSA results in an obvious hysteretic effect on the fluorescence of BSA. The time-dependent fluorescence quenching of BSA by Fe(2+) is not caused by the Fe(2+)-induced conformational change of BSA, but the oxygen-dependent oxidation of Fe(2+) to Fe(3+). Fe(2+) undergoes an oxygen-dependent oxidation to Fe(3+) under aerobic conditions, which is accelerated by the interaction of BSA with Fe(3+) and extensively inhibited under anaerobic conditions. The results suggest that BSA may take part in non-transferrin bound iron transfer.
authors.affiliation: Department of Chemistry, University of Science and Technology of China, Hefei 230026, People's Republic of China. xuxl@ustc.edu.cn
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Xu
authors.forename: Liyun
authors.initials: L
authors.lastname: Zhang
authors.forename: Dengke
authors.initials: D
authors.lastname: Shen
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.forename: Qingliang
authors.initials: Q
authors.lastname: Liu
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D005453:Fluorescence; D010084:Oxidation-Reduction / Q000187:drug effects*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D012710:Serum Albumin, Bovine; D014364:Tryptophan; D010100:Oxygen