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Journal of Bacteriology, January 2002, p. 165-170, Vol. 184, No. 1
0021-9193/01/$04.00+0     DOI: 10.1128/JB.184.1.165-170.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

The Active Component of the Bioemulsifier Alasan from Acinetobacter radioresistens KA53 Is an OmpA-Like Protein

Amir Toren,¹ Elisha Orr,² Yossi Paitan,¹ Eliora Z. Ron,¹ and Eugene Rosenberg^1*

Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel 69978,¹ Department of Genetics, University of Leicester, Leicester LE1 7RH, United Kingdom²

Received 2 July 2001/ Accepted 25 September 2001

The bioemulsifier of Acinetobacter radioresistens KA53, referred to as alasan, is a high-molecular-weight complex of polysaccharide and protein. Recently, one of the alasan proteins, with an apparent molecular mass of 45 kDa, was purified and shown to constitute most of the emulsifying activity. The N-terminal sequence of the 45-kDa protein showed high homology to an OmpA-like protein from Acinetobacter spp. In the research described here the gene coding for the 45-kDa protein was cloned, sequenced, and expressed in Escherichia coli. Recombinant protein AlnA (35.77 kDa without the leader sequence) had an amino acid sequence homologous to that of E. coli OmpA and contained 70% of the specific (hydrocarbon-in-water) emulsifying activity of the native 45-kDa protein and 2.4 times that of the alasan complex. In addition to their emulsifying activity, both the native 45-kDa protein and the recombinant AlnA were highly effective in solubilizing phenanthrene, ca. 80 µg per mg of protein, corresponding to 15 to 19 molecules of phenanthrene per molecule of protein. E. coli OmpA had no significant emulsifying or phenanthrene-solubilizing activity. The production of a recombinant surface-active protein (emulsification and solubilization of hydrocarbons in water) from a defined gene makes possible for the first time structure-function studies of a bioemulsan.

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* Corresponding author. Mailing address: Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel 69978. Phone: 972-3-640 9838. Fax: 972-3-642 9377. E-mail: eros{at}ccsg.tau.ac.il.

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Journal of Bacteriology, January 2002, p. 165-170, Vol. 184, No. 1
0021-9193/01/$04.00+0     DOI: 10.1128/JB.184.1.165-170.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

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