A retroviral Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys peptide binds metal ions: spectroscopic studies and a proposed three-dimensional structure.
Retroviral gag gene-encoded core nucleic acid binding proteins contain either one or two sequences of the form Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys. Previously, one of us has proposed that these sequences form metal-binding domains in analogy with the "zinc finger" domains first observed in transcription factor IIIA. We report that an 18-amino acid peptide derived from the core nucleic acid binding protein from Rauscher murine leukemia virus binds metal ions such as Co2+ and Zn2+. The absorption spectrum of the peptide-Co2+ complex is highly suggestive of tetrahedral coordination involving three cysteinates and one histidine. Titration experiments indicate that the dissociation constant for the peptide-Co2+ complex is 1.0 microM and that Zn2+ binds more tightly than Co2+. A detailed three-dimensional structure for this domain based on conserved substructures in other crystallographically characterized metalloproteins and on a detailed analysis of the Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys sequences from retroviruses and other related sources is proposed.
Green
L M
LM
Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218.
Berg
J M
JM
D000595:Amino Acid Sequence; D015683:Gene Products, gag; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis*; D011487:Protein Conformation; D012190:Retroviridae / Q000235:genetics; D012191:Retroviridae Proteins / Q000235:genetics* / Q000378:metabolism
D015683:Gene Products, gag; D009842:Oligopeptides; D012191:Retroviridae Proteins