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Journal of Bacteriology, January 2000, p. 295-302, Vol. 182, No. 2
Laboratory of Molecular Biotechnology,
Graduate School of Biological and Agricultural Sciences, Nagoya
University, Chikusa-ku, Nagoya 464-8601, Japan
Received 7 July 1999/Accepted 27 October 1999
The expression of lipase from Pseudomonas sp. strain
KWI-56 (recently reclassified as Burkholderia cepacia) had
been found to be dependent on an activator gene (act)
downstream of its structural gene (lip). In this work, the
mature lipase was synthesized in an enzymatically active form with a
cell-free Escherichia coli S30 coupled
transcription-translation system by expressing a recombinant lipase
gene (rlip) encoding the mature lipase in the presence of
its purified activator or by coexpression of rlip and
act. The in vitro expression systems were used for studying
the folding process of the lipase. The addition of dithiothreitol in
the expression systems decreased the activity dramatically without
affecting the synthesis level of the lipase, whereas the in
vitro-synthesized active lipase was relatively stable even in the
presence of dithiothreitol. This phenomenon was further investigated by
constructing mutant lipase genes only in vitro by PCR without gene
cloning. Replacements of cysteine residues (Cys190 and Cys270) forming
a sole putative disulfide bond to serine residues decreased the lipase
activity greatly, suggesting that the disulfide bond was essential for the proper folding of the lipase. In addition, replacing Asp242 and
Asp288, which were deduced to be part of a Ca2+ binding
site, also greatly decreased the activities of the in vitro-synthesized
lipases. The role of the Ca2+ binding site in the
activation of the lipase is also discussed.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
In Vitro Analysis of Roles of a Disulfide Bridge and a Calcium
Binding Site in Activation of Pseudomonas sp. Strain
KWI-56 Lipase
*
Corresponding author. Mailing address: Laboratory of
Molecular Biotechnology, Graduate School of Biological and Agricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. Phone: 81-52-789-4143. Fax: 81-52-789-4145. E-mail:
hnakano{at}agr.nagoya-u.ac.jp.
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