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Applied and Environmental Microbiology, April 2000, p. 1572-1579, Vol. 66, No. 4
Department I of Internal Medicine, University
of Cologne, Cologne,1 and Institute of
Biochemistry, University of Münster,
Münster,2 Germany
Received 12 October 1999/Accepted 16 January 2000
The standard method of producing recombinant proteins such as
immunotoxins (rITs) in large quantities is to transform gram-negative bacteria and subsequently recover the desired protein from inclusion bodies by intensive de- and renaturing procedures. The major
disadvantage of this technique is the low yield of active protein. Here
we report the development of a novel strategy for the expression of
functional rIT directed to the periplasmic space of Escherichia coli. rITs were recovered by freeze-thawing of pellets from
shaking cultures of bacteria grown under osmotic stress (4% NaCl plus 0.5 M sorbitol) in the presence of compatible solutes. Compatible solutes, such as glycine betaine and hydroxyectoine, are
low-molecular-weight osmolytes that occur naturally in halophilic
bacteria and are known to protect proteins at high salt concentrations.
Adding 10 mM glycine betaine for the cultivation of E. coli
under osmotic stress not only allowed the bacteria to grow under these
otherwise inhibitory conditions but also produced a periplasmic
microenvironment for the generation of high concentrations of correctly
folded rITs. Protein purified by combinations of metal ion affinity and size exclusion chromatography was substantially stabilized in the
presence of 1 M hydroxyecotine after several rounds of freeze-thawing, even at very low protein concentrations. The binding properties and
cytotoxic potency of the rITs were confirmed by competitive experiments. This novel compatible-solute-guided expression and purification strategy might also be applicable for high-yield periplasmic production of recombinant proteins in different expression systems.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Compatible-Solute-Supported Periplasmic Expression
of Functional Recombinant Proteins under Stress Conditions
*
Corresponding author. Mailing address: Medizinische
Klinik I der Universität zu Köln, Labor für
Immuntherapie, Joseph-Stelzmann-Str. 9, D-50931 Köln, Germany.
Phone: 49 (0) 221 478-3593. Fax: 49 (0) 221 478-6383. E-mail:
stefan.barth{at}uni-koeln.de.
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