Recombinant expression and characterization of an extremely hyperthermophilic archaeal histone from Pyrococcus horikoshii OT3

Abstract A histone-like gene, PHS051 from hyperthermophilic archaeon Pyrococcus horikoshii OT3 strain, was cloned, sequenced, and expressed in Escherichia coli . The recombinant histone, HPhA, encodes a protein of 70 amino acids with a molecular weight of 7868 Da. Amino acid sequence analysis of HPhA showed high homology with other archaeal histones and eukaryal core histones. The HPhA was purified to homogeneity by heat precipitation and affinity chromatography. Gel electrophoresis mobility shift assays demonstrate that the purified HPhA has high affinity to DNA. The complex of the HPhA and DNA allows DNA to be protected from cleavage by the restriction enzyme Taq I at 65 °C. Circular dichroism spectra reveal that the conformation of the recombinant histone HPhA becomes looser when temperatures increase from 25 to 90 °C. The HPhA has inherited a remarkable thermostability especially in the presence of 1 M KCl and retained DNA binding activity at extreme temperature, which is consistent with our previous report about its structure stability analyzed by X-ray crystallography.