The TolC-like protein HgdD of the cyanobacterium Anabaena sp. PCC 7120 is involved in secondary metabolite export and antibiotic resistance.
The role of TolC has largely been explored in proteobacteria, where it functions as a metabolite and protein exporter. In contrast, little research has been carried out on the function of cyanobacterial homologues, and as a consequence, not much is known about the mechanism of cyanobacterial antibiotic uptake and metabolite secretion in general. It has been suggested that the TolC-like homologue of the filamentous, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120, termed heterocyst glycolipid deposition protein D (HgdD), is involved in both protein and lipid secretion. To describe its function in secondary metabolite secretion, we established a system to measure the uptake of antibiotics based on the fluorescent molecule ethidium bromide. We analyzed the rate of porin-dependent metabolite uptake and confirmed the functional relation between detoxification and the action of HgdD. Moreover, we identified two major facilitator superfamily proteins that are involved in this process. It appears that anaOmp85 (Alr2269) is not required for insertion or assembly of HgdD, because an alr2269 mutant does not exhibit a phenotype similar to the hgdD mutant. Thus, we could assign components of the metabolite efflux system and describe parameters of detoxification by Anabaena sp. PCC 7120.
Department of Biosciences, Center of Membrane Proteomics, Cluster of Excellence Frankfurt, Goethe University, 60438 Frankfurt, Germany.
Alexander
A
Hahn
Mara
M
Stevanovic
Oliver
O
Mirus
Enrico
E
Schleiff
D017033:Anabaena / Q000378:metabolism*; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D001667:Binding, Competitive; D001692:Biological Transport; D004352:Drug Resistance, Microbial / Q000235:genetics; D029968:Escherichia coli Proteins; D004996:Ethidium / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D026901:Membrane Transport Proteins; D008954:Models, Biological; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D018272:Porins / Q000737:chemistry; D013045:Species Specificity
D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D018272:Porins; C073126:tolC protein, E coli; D004996:Ethidium