title: Cisplatin binding sites on human albumin.
abstract: Reactions of cisplatin (cis-[PtCl2(NH3)2]) with albumin are thought to play an important role in the metabolism of this anticancer drug. They are investigated here via (i) labeling of cisplatin with 15N and use of two-dimensional 1H,15N NMR spectroscopy, (ii) comparison of natural human serum albumin with recombinant human albumin (higher homogeneity and SH content), (iii) chemical modification of Cys, Met, and His residues, (iv) reactions of bound platinum with thiourea, and (v) gel filtration chromatography. In contrast to previous reports, it is shown that the major sulfur-containing binding site involves Met and not Cys-34, and also a N ligand, in the form of an S,N macrochelate. Additional monofunctional adducts involving other Met residues and Cys-34 are also observed. During the later stages of reactions of cisplatin with albumin, release of NH3 occurs due to the strong trans influence of Met sulfur, which weakens the Pt-NH3 bonds, and protein cross-linking is observed. The consequences of these findings for the biological activity of cisplatin-albumin complexes are discussed.
authors.affiliation: Department of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, United Kingdom.
authors.forename: A I
authors.initials: AI
authors.lastname: Ivanov
authors.forename: J
authors.initials: J
authors.lastname: Christodoulou
authors.forename: J A
authors.initials: JA
authors.lastname: Parkinson
authors.forename: K J
authors.initials: KJ
authors.lastname: Barnham
authors.forename: A
authors.initials: A
authors.lastname: Tucker
authors.forename: J
authors.initials: J
authors.lastname: Woodrow
authors.forename: P J
authors.initials: PJ
authors.lastname: Sadler
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000970:Antineoplastic Agents / Q000378:metabolism; D001665:Binding Sites; D002712:Chlorides / Q000494:pharmacology; D002850:Chromatography, Gel; D002945:Cisplatin / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000378:metabolism; D009587:Nitrogen Isotopes; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D012709:Serum Albumin / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000032:analysis; D013890:Thiourea / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D002712:Chlorides; D009587:Nitrogen Isotopes; D011994:Recombinant Proteins; D012709:Serum Albumin; D013438:Sulfhydryl Compounds; D000641:Ammonia; D008715:Methionine; D013890:Thiourea; D003545:Cysteine; D002945:Cisplatin