Role of the histidine residues of visna virus nucleocapsid protein in metal ion and DNA binding

Zinc finger (ZF) domains in retroviral nucleocapsid proteins usually contai n one histidine per metal ion coordination complex (Cys-X-2-Cys-X-4-His-X-4 -Cys). Visna virus nucleocapsid protein, p8, has two additional histidines (in the second of its two ZFs) that could potentially bind metal ions. Abso rption spectra of cobalt-bound ZF2 peptides were altered by Cys alkylation and mutation, but not by mutation of the extra histidines. Our results show that visna p8 ZFs involve three Cys and one His in the canonical spacing i n metal ion coordination, and that the two additional histidines appear to interact with nucleic acid bases in p8-DNA complexes. (C) 2000 Federation o f European Biochemical Societies. Published by Elsevier Science B.V. All ri ghts reserved.