The active component of the bioemulsifier alasan from Acinetobacter radioresistens KA53 is an OmpA-like protein.
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 microg 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.
Toren
Amir
A
Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel 69978.
Orr
Elisha
E
Paitan
Yossi
Y
Ron
Eliora Z
EZ
Rosenberg
Eugene
E
D000150:Acinetobacter / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics*; D005079:Excipients / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D010616:Phenanthrenes; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000235:genetics*; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D012995:Solubility
C443986:AlnA protein, Acinetobacter radioresistens; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D005079:Excipients; D010616:Phenanthrenes; D011135:Polysaccharides, Bacterial; D011994:Recombinant Proteins; C443985:alasan protein, Acinetobacter radioresistens; C078167:OMPA outer membrane proteins; C031181:phenanthrene