Histone–histone interactions. II. Structural stability of the histone H3–H4 complex

Abstract

The stability of the [calf thymus] histone H3-H4 complex toward urea, changes in pH and ionic strength, and certain chemical modifications were examined by gel electrophoresis and circular dichroism. When uncomplexed the 2 cysteine residues of histone H3 become rapidly oxidized, forming an intramolecular disulfide bridge which apparently blocks complex formation on return to complexing conditions. The complex was unstable toward low values of pH and ionic strength, concentrations of urea exceeding 1 M, modifications of the cysteine residues, and fragmentation in which the C terminal portions of either H3 or H4 are removed. A possible structure for this complex is proposed.