Histones and Metal-Binding Domains

Jeremy M. Berg (1) describes potential -binding domains in nucleic acid-binding . These metal-binding domains of sequences Cys-X_(2-4)-Cys-X_(4-15)-His-X_(2-8)-Cys. Berg also cites the fact proteins known to bind ions have short of the form Cys-X_(2-4)-Cys, Cys-X_(2-4)-His, or His-X_(2-3)-His. A well-known -binding protein, histone H3, also has conserved sequence Cys-Ala-Ile-His residues 110 to 113 (2). The nucleosome has two histones of each kind four histones. These histones are organized an axis of symmetry, such that conserved sequences on each histone 3 oppose each other (3). The apposition these two histone H3 sequences would a structure potentially able to coordinate metal ion, namely 2(Cys-Ala-Ile-His).