Method for preparing and purifying ubiquitination or ubiquitination-like histone octamer by utilizing chemical crosslinking

The invention discloses a method for preparing and purifying a ubiquitination or ubiquitination-like histone octamer by utilizing chemical crosslinking. The method comprises the following steps: (1) expressing and purifying to obtain mutant ubiquitin or ubiquitination-like protein; the C terminal of the mutant ubiquitin is cysteine, and a nucleotide sequence corresponding to glycine at the C terminal of the mutant ubiquitin-like protein is mutated into a nucleotide sequence corresponding to cysteine; (2) expressing and purifying to obtain a mutant histone octamer; the lysine on the ubiquitination/ubiquitination-like modification site of the mutant histone octamer is mutated into cysteine; (3) carrying out cross-linking reaction on the mutant ubiquitin or ubiquitin-like protein and the mutant histone octamer under a non-denaturing condition by utilizing a chemical cross-linking agent; and (4) carrying out standard chromatographic purification on the chemical cross-linking reaction product. According to the met