title: Interaction of cisplatin with methionine- and histidine-containing peptides: competition between backbone binding, macrochelation and peptide cleavage.
abstract: The pH- and time-dependent reaction of cis-[PtCl2(NH3)2] with the methionine- and histidine-containing peptides H-Gly-Met-OH, H-Gly-Gly-Met-OH, Ac-His-Gly-Met-OH, and Ac-His-(Ala)3-Met-OH at 313 K has been investigated by ion-pairing reverse phase HPLC and NMR spectroscopy. For equimolar solutions (c=0.8 mM, pH approximately equals 3 or 8.8), initial formation of the kinetically favored S-bound complex is followed by relatively rapid metallation of the neighboring methionine amide nitrogen NM to afford a kappa2NM,S six-membered chelate. The strong trans effect of the methionine S then favors facile NH3 substitution, leading to generation of tridentate complexes such as [Pt(H-Gly-MetH(-1)-OH)-kappa3NG,NM,S)(NH3)]+ or [Pt(H-Ac-His-GlyH(-1)-MetH(-1)-OH-kappa3NG,NM,S)(NH3)]. In the case of H-Gly-Gly-Met-OH, this reaction is accompanied by loss of a second NH3 ligand in alkaline solution to generate the tetradentate kappa4NG1,NG2,NM,S species. In contrast, cleavage of the backbone C(O)-N bond to the second metallated amide nitrogen after t>100 h is common to the tridentate complexes of the tri- and pentapeptides at pH<5. Although an imidazole-coordinated kappa2N3H,S macrochelate is formed throughout the whole range 2.5 < or = pH < or = 10 for Ac-His-Gly-Met-OH, it slowly decays (t=10-1000 h) to the thermodynamically more stable tridentate kappa3NG,NM,S complex. All major final products were separated and fully characterized by NMR and MS.
authors.affiliation: Lehrstuhl für Analytische Chemie, Ruhr-Universität Bochum, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hahn
authors.forename: M
authors.initials: M
authors.lastname: Kleine
authors.forename: W S
authors.initials: WS
authors.lastname: Sheldrick
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive; D002851:Chromatography, High Pressure Liquid; D002945:Cisplatin / Q000737:chemistry / Q000378:metabolism*; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D010455:Peptides; D006639:Histidine; D008715:Methionine; D002945:Cisplatin