Insoluble expression of highly soluble halophilic metal binding protein for metal ion biosorption: Application of aggregation-prone peptide from hen egg white lysozyme

Insoluble expression of intrinsically soluble proteins with native activity is potentially a promising alternative to soluble expression of folded protein or insoluble expression of unfolded protein requiring refolding. Here, we attempted to express highly soluble halophilic His-rich metal binding protein (HP) as insoluble inclusion bodies with native metal-binding activity using insolubilizing nona-peptide (Ins), GILQINSRW, derived from hen egg white lysozyme (His-InsHP). About 80% of expressed His-InsHP was localized in inclusion bodies in Na-phosphate/NaCl buffer, pH 7.4, while His-HP without Ins peptide was exclusively expressed in soluble supernatant. We report expression, purification and characterization of this insoluble His-InsHP, and its possible application for efficient biosorption and recovery of environmental metal ions, for example, by using whole bacterial cells expressing insoluble His-insHP as a new cost-effective metal ion-adsorbent.