Human T-lymphotrophic virus type I nucleocapsid protein NCp15: structural study and stability of the N-terminal zinc-finger

Abstract

An 18-residue peptide, corresponding to the minimum sequence of the N-terminal zinc-finger domain in the nucleocapsid of human T-lymphotrophic virus type I, was synthesized by a solid-phase method and fully characterized. Its ability to complex metal ions (Co2+ and Zn2+) was clearly established by UV–visible spectroscopy and MS. The stability of these complexes was investigated by an original method with HPLC chromatography. Our results show that, even in the presence of air, the Zn2+ complex is highly stable. In contrast, the Co2+ complex undergoes a relatively fast degradation due to an intramolecular oxidation leading to the formation of a disulphide bridge between two cysteine residues. The 1H-NMR analysis indicates that Zn2+ binds to the Nδ atom of the histidine residue rather than to the Nε atom. Two-dimensional NMR techniques were used to determine the solution structure of the zinc-finger, illustrated by the existence of turns in the overall conformation.