Interaction of cisplatin with a CCHC zinc finger motif

The interaction between cisplatin and an 18-residue CCHC zinc finger motif derived from a retroviral nucleocapsid protein (PyrZf18) has been studied using UV-visible, CD and (1)H NMR spectroscopies and ESI-MS spectrometry. Cisplatin irreversibly blocks the cysteine zinc binding groups in the free peptide and is able to slowly eject zinc from the zinc-peptide complex. The observed end product of the reaction with cisplatin is a complex in which only one ammonia molecule is coordinated to platinum. After an initial binding with two cysteine residues and the formation of the (PyrZf18)-platinum-(NH3)2 complex, a release of one ammonia molecule occurs because of trans-labilization, and the third cysteine is coordinated, leading to a mixture of isomers and/or conformers of the (PyrZf18)-platinum-NH3 complex. The results are discussed with respect to the potential antiretroviral activity of platinum(II) compounds and to the possible interaction of cisplatin with the cellular nucleic acid binding proteins.