We amplified the coding regions of the previously cloned HI genes HI-I
, HI degrees and HIt and inserted them into the expression vector pET-
IId. The synthesis of the HI histones can be induced in the appropriat
e strains of bacteria, and the HI histones can be readily purified. We
report detailed protocols for the purification of the expressed prote
ins using combinations of ion-exchange and reverse-phase HPLC. Suffici
ent amounts of each pure variant protein can be obtained for use in ph
ysical studies of HI-DNA interactions.