Open AccessIn Vitro Folding of Escherichia Coli Outer‐Membrane Phospholipase A
Author(s) -
Dekker Niek,
Merck Karin,
Tommassen Jan,
Verheij Hubertus M.
Publication year - 1995
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1995.tb20801.x
Subject(s) - circular dichroism , escherichia coli , biochemistry , bacterial outer membrane , enzyme , inclusion bodies , protein folding , recombinant dna , chemistry , membrane , biology , gene
Recombinant outer‐membrane phospholipase A (OMPLA) of Escherichia coli was expressed without its signal sequence from the T7φ10 promoter. As a result of the cloning strategy the protein had an N‐terminal extension of six amino acid residues. The protein accumulated in the cytosol in inclusion bodies. Conditions were established for the efficient folding of OMPLA in vitro in the presence of Triton X‐100. After in vitro folding, the protein was present as a mixture of folded and unfolded forms. Ion‐exchange chromatography was used for the purification of OMPLA and the separation of correctly folded, enzymically active enzyme from unfolded inactive protein. The final protein preparation was pure and fully heat‐modifiable based on SDS/PAGE. The recombinant enzyme had a specific activity of 71 U/mg, which is similar to the value of the wild‐type enzyme, purified from the membrane. The final yield of active enzyme was 35 mg protein/1 culture of an A 600 of 6. Circular dichroism spectroscopy revealed a high content of β strand, in good agreement with a predicted β‐barrel structure of this outer‐membrane protein.