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1.B.13 The Alginate Export Porin (AEP) Family

Only two proteins of the AEP family have been sequenced, AlgE of Pseudomonas aeruginosa and AlgJ of Azotobacter vinelandii. Both proteins are believed to export the acidic polysaccharide, alginate, across the outer membrane of these Gram-negative bacteria. These proteins possess 490 and 484 amino acyl residues, are 50% identical, and are predicted to span the outer membrane 18 times as β-strands, thereby forming a β-barrel. The P. aeruginosa protein has been shown to form an anion-selective channel after incorporation into an artificial planar lipid bilayer. It may function in the export of polymannuronic acid, a precursor of alginate.

The generalized transport reaction normally catalyzed by proteins of the AEP family is:

Alginate (periplasm) → Alginate (out)

References associated with 1.B.13 family:

Manilla-Pérez, E., C. Reers, M. Baumgart, S. Hetzler, R. Reichelt, U. Malkus, R. Kalscheuer, M. Wältermann, and A. Steinbüchel. (2010). Analysis of lipid export in hydrocarbonoclastic bacteria of the genus Alcanivorax: identification of lipid export-negative mutants of Alcanivorax borkumensis SK2 and Alcanivorax jadensis T9. J. Bacteriol. 192: 643-656. 19933359
Rehm, B.H., G. Boheim, J. Tommassen, and U.K. Winkler. (1994). Overexpression of algE in Escherichia coli: subcellular localization, purification, and ion channel properties. J. Bacteriol. 176: 5639-5647. 7521870
Rehm, B.H.A. (1996). The Azotobacter vinelandii gene algJ encodes an outer-membrane protein presumably involved in export of alginate. Microbiol. 142: 873-880. 8936313
Rehman ZU. and Rehm BH. (2013). Dual roles of Pseudomonas aeruginosa AlgE in secretion of the virulence factor alginate and formation of the secretion complex. Appl Environ Microbiol. 79(6):2002-11. 23335756