DipA, a pore-forming protein in the outer membrane of Lyme disease spirochetes exhibits specificity for the permeation of dicarboxylates

• Published in: PloS one 2012-05, Vol.7 (5), p.e36523-e36523
• Main Authors: Thein, Marcus, Bonde, Mari, Bunikis, Ignas, Denker, Katrin, Sickmann, Albert, Bergström, Sven, Benz, Roland
• Format: Article
• Language: English
• Subjects: a-Ketoglutaric acid; Amino acids; Animals; Anions; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Biology; Borrelia; Borrelia - genetics; Borrelia - metabolism; Borrelia burgdorferi; Brain research; Cations; Cell Membrane Permeability - physiology; Chlorides; Chromatography; Citric acid; Conductance; Dicarboxylic Acid Transporters - genetics; Dicarboxylic Acid Transporters - metabolism; E coli; Escherichia coli; Exhibitions; Fever; Genomes; Genomics; Homology; Humans; Hydroxyapatite; Hydroxyapatites; Ketoglutaric acid; Lipids; Localization; Lyme disease; Lyme Disease - genetics; Lyme Disease - metabolism; Mass spectrometry; Medicine; Membrane lipids; Membrane proteins; Membranes; Metabolism; Molecular biology; Nutrients; Permeability; Pore formation; Porins; Potassium chloride; Proteins; Rabbits; Relapsing fever; Resistance; Scientific imaging; Sequence Homology, Amino Acid; Spirochetes; Stability constants; Substrate Specificity; Trends; Vector-borne diseases
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0036523

Lyme disease Borreliae are highly dependent on the uptake of nutrients provided by their hosts. Our study describes the identification of a 36 kDa protein that functions as putative dicarboxylate-specific porin in the outer membrane of Lyme disease Borrelia. The protein was purified by hydroxyapatite chromatography from Borrelia burgdorferi B31 and designated as DipA, for dicarboxylate-specific porin A. DipA was partially sequenced, and corresponding genes were identified in the genomes of B. burgdorferi B31, Borrelia garinii PBi and Borrelia afzelii PKo. DipA exhibits high homology to the Oms38 porins of relapsing fever Borreliae. B. burgdorferi DipA was characterized using the black lipid bilayer assay. The protein has a single-channel conductance of 50 pS in 1 M KCl, is slightly selective for anions with a permeability ratio for cations over anions of 0.57 in KCl and is not voltage-dependent. The channel could be partly blocked by different di- and tricarboxylic anions. Particular high stability constants up to about 28,000 l/mol (in 0.1 M KCl) were obtained among the 11 tested anions for oxaloacetate, 2-oxoglutarate and citrate. The results imply that DipA forms a porin specific for dicarboxylates which may play an important role for the uptake of specific nutrients in different Borrelia species.