Journal of Bacteriology, March 1999, p. 1847-1852, Vol. 181, No. 6
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Department of Biological Sciences,
Received 30 October 1998/Accepted 5 January 1999
Pseudomonas fluorescens, a gram-negative psychrotrophic
bacterium, secretes a thermostable lipase into the extracellular
medium. In our previous study, the lipase of P. fluorescens
SIK W1 was cloned and expressed in Escherichia coli, but it
accumulated as inactive inclusion bodies. Amino acid sequence analysis
of the lipase revealed a potential C-terminal targeting sequence
recognized by the ATP-binding cassette (ABC) transporter. The genetic
loci around the lipase gene were searched, and a secretory gene was identified. Nucleotide sequencing of an 8.5-kb DNA fragment revealed three components of the ABC transporter, tliD,
tliE, and tliF, upstream of the lipase gene,
tliA. In addition, genes encoding a protease and a protease
inhibitor were located upstream of tliDEF. tliDEF showed high similarity to ABC transporters of
Pseudomonas aeruginosa alkaline protease, Erwinia
chrysanthemi protease, Serratia marcescens lipase,
and Pseudomonas fluorescens CY091 protease. tliDEF and the lipase structural gene in a single operon
were sufficient for E. coli cells to secrete the
lipase. In addition, E. coli harboring the lipase gene
secreted the lipase by complementation of tliDEF in a
different plasmid. The ABC transporter of P. fluorescens was optimally functional at 20 and 25°C, while the ABC transporter, aprD, aprE, and aprF, of P. aeruginosa secreted the lipase irrespective of temperature
between 20 and 37°C. These results demonstrated that the lipase is
secreted by the P. fluorescens SIK W1 ABC transporter, which is organized as an operon with tliA, and that its
secretory function is temperature dependent.
*
Corresponding author. Mailing address: Department of
Biological Sciences, Korea Advanced Institute of Science and
Technology, 373-1, Kusong-Dong, Yusong-Gu, Taejon 305-701, Korea.
Phone: 82-42-869-2613. Fax: 82-42-869-2610. E-mail:
jsrhee{at}sorak.kaist.ac.kr.
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