UBL5, also known ubiquitin-like protein 5, is thought to be reversible modulators of protein function rather than protein degraders like ubiquitin. This protein effects a nuclear step required for mounting a response to the threat of mitochondrial protein misfolding. Recombinant human UBL5 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.