title: Hyper-acidic protein fusion partners improve solubility and assist correct folding of recombinant proteins expressed in Escherichia coli.
abstract: High expression of recombinant proteins in Escherichia coli (E. coli) often leads to protein aggregation. One popular approach to address this problem is the use of fusion tags (or partners) that improve the solubility of the proteins in question. However, such fusion tags are not effective for all proteins. In this study, we demonstrate that the hyper-acidic protein fusion partners can largely enhance the soluble expression of target proteins recalcitrant to the efforts by using routine solubilising tags. This new type of fusion partners examined includes three extremely acidic E. coli polypeptides, i.e. yjgD, the N-terminal domain of rpoD (sigma 70 factor of RNA polymerase) and our preliminarily evaluated msyB. The target proteins used are highly aggregation-prone, including EK (the bovine enterokinase), TEV (the tobacco etch virus protease) and rbcL (the large subunit of tobacco ribulose-1,5-bisphosphate carboxylase/oxygenase). On removal in vitro and in vivo of the fusion tags by using yeast SUMO/Ulp1 reaction and TEV auto-cleavage, the resultant findings indicate the hyper-acidic fusion partners can function as intramolecular chaperones assisting in the correct folding of the target proteins.
authors.affiliation: School of Life Sciences, East China Normal University, North Zhongshan Road 3663, Shanghai 200062, China. zrzou@bio.ecnu.edu.cn
authors.forename: Zhurong
authors.initials: Z
authors.lastname: Zou
authors.forename: Lijuan
authors.initials: L
authors.lastname: Cao
authors.forename: Pei
authors.initials: P
authors.lastname: Zhou
authors.forename: Yu
authors.initials: Y
authors.lastname: Su
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Sun
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Li
mesh_terms: D003546:Cysteine Endopeptidases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D005822:Genetic Vectors; D018832:Molecular Chaperones / Q000378:metabolism; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D012995:Solubility
chemical_list: D018832:Molecular Chaperones; D011993:Recombinant Fusion Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D010450:Endopeptidases; C099488:TEV protease; D003546:Cysteine Endopeptidases; C118083:Ulp1 protease