Optimized E. coli expression strain LOBSTR eliminates common contaminants from His-tag purification

Proteins. 2013 Nov;81(11):1857-61. doi: 10.1002/prot.24364. Epub 2013 Aug 23.


His-tag affinity purification is one of the most commonly used methods to purify recombinant proteins expressed in E. coli. One drawback of using the His-tag is the co-purification of contaminating histidine-rich E. coli proteins. We engineered a new E. coli expression strain, LOBSTR (low background strain), which eliminates the most abundant contaminants. LOBSTR is derived from the E. coli BL21(DE3) strain and carries genomically modified copies of arnA and slyD, whose protein products exhibit reduced affinities to Ni and Co resins, resulting in a much higher purity of the target protein. The use of LOBSTR enables the pursuit of challenging low-expressing protein targets by reducing background contamination with no additional purification steps, materials, or costs, and thus pushes the limits of standard His-tag purifications.

Keywords: BL21(DE3); E. coli protein expression strain; His-tag affinity purification; LOBSTR.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Affinity
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Histidine / chemistry*
  • Recombinant Proteins / chemistry*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism*


  • Escherichia coli Proteins
  • Recombinant Proteins
  • Histidine