title: Streamlined protein expression and purification using cleavable self-aggregating tags.
abstract: BACKGROUND
  Recombinant protein expression and purification remains a fundamental issue for biotechnology. Recently we found that two short self-assembling amphipathic peptides 18A (EWLKAFYEKVLEKLKELF) and ELK16 (LELELKLKLELELKLK) can induce the formation of active protein aggregates in Escherichia coli (E. coli), in which the target proteins retain high enzymatic activities. Here we further explore this finding to develop a novel, facile, matrix-free protein expression and purification approach.
  
  
  RESULTS
  In this paper, we describe a streamlined protein expression and purification approach by using cleavable self-aggregating tags comprising of one amphipathic peptide (18A or ELK16) and an intein molecule. In such a scheme, a target protein is first expressed as active protein aggregate, separated by simple centrifugation, and then released into solution by intein-mediated cleavage. Three target proteins including lipase A, amadoriase II and β-xylosidase were used to demonstrate the feasibility of this approach. All the target proteins released after cleavage were highly active and pure (over 90% in the case of intein-ELK16 fusions). The yields were in the range of 1.6-10.4 μg/mg wet cell pellet at small laboratory scale, which is comparable with the typical yields from the classical his-tag purification, the IMPACT-CN system (New England Biolabs, Beverly, MA), and the ELP tag purification scheme.
  
  
  CONCLUSIONS
  This tested single step purification is capable of producing proteins with high quantity and purity. It can greatly reduce the cost and time, and thus provides application potentials for both industrial scale up and laboratorial usage.
authors.affiliation: Department of Chemical Engineering, Tsinghua University, One Tsinghua Garden Road, Beijing 100084, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Xing
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Bihong
authors.initials: B
authors.lastname: Zhou
authors.forename: Zhanglin
authors.initials: Z
authors.lastname: Lin
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism; D047668:Inteins / Q000235:genetics; D008049:Lipase / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D014995:Xylosidases / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification
chemical_list: D010455:Peptides; D011993:Recombinant Fusion Proteins; C080383:peptide 18A; D000594:Amino Acid Oxidoreductases; C103012:amadoriase; D008049:Lipase; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase