3-DIMENSIONAL H-1-NMR STRUCTURE OF THE NUCLEOCAPSID PROTEIN NCP10 OF MOLONEY MURINE LEUKEMIA-VIRUS

The nucleocapsid protein of Moloney murine leukemia virus (NCp10) is a 56-amino acid protein which contains one zinc finger of the CysX2CvsX 4HisX4Cys form, a highly conserved motif present in most retroviruses and retroelements. At pH greater-than-or-equal-to 5, NCp10 binds one z inc atom and the complexation induces a folding of the CysX2CysX4HisX4 Cys box, similar to that observed for the zinc-binding domains of HIV- 1 NC protein. The three-dimensional structure of NCp10 has been determ ined in aqueous solution by 600 MHz H-1 NMR spectroscopy. The proton r esonances could be almost completely assigned by means of phase-sensit ive double-quantum-filtered COSY, TOCSY and NOESY techniques. NOESY sp ectra yielded 597 relevant structural constraints, which were used as input for distance geometry calculations with DIANA. Further refinemen t was performed by minimization with the program AMBER, which was modi fied by introducing a zinc force field. The solution structure is char acterized by a well-defined central zinc finger (rmsd of 0.747 +/- 0.2 09 angstrom for backbone atoms and 1.709 +/- 0.187 angstrom when all a toms are considered), surrounded by flexible N- and C-terminal domains . The Tyr28 , Trp35, Lys37, LYS41 and Lys42 residues, which are essent ial for activity, lie on the same face of the zinc finger, forming a b ulge structure probably involved in viral RNA binding. The significanc e of these structural characteristics for the various biological funct ions of the protein is discussed, taking into account the results obta ined with various mutants.