Transport of multidrug resistance substrates by the Streptococcus agalactiae hemolysin transporter.
Streptococcus agalactiae (group B streptococcus [GBS]) causes neonatal sepsis, pneumonia, and meningitis, as well as infections of the bovine udder. The S. agalactiae hemolysin is regarded as an important virulence factor, and hemolysin expression is dependent on the cyl gene cluster. cylA and cylB encode the ATP binding and transmembrane domains of a typical ATP binding cassette (ABC) transporter. The deduced proteins contain the signature sequence of a multidrug resistance (MDR) transporter, and mutation of the genes results in a nonhemolytic and nonpigmented phenotype. To further elucidate the function of the putative transporter, nonpolar deletion mutants of cylA were constructed. These mutants are nonhemolytic and can be complemented by the transporter genes. Wild-type strain and nonhemolytic cylA and cylK deletion mutants were exposed to known substrates of MDR transporters. Mutation of cylA significantly impaired growth in the presence of daunorubicin, doxorubicin, and rhodamine 6G and resulted in a decreased export of doxorubicin from the cells. The mutation of cylK, a gene of unknown function located downstream from cylA, caused a loss of hemolysis but had no effect on the transport of MDR substrates. Furthermore, the hemolytic activity of the wild-type strain was inhibited by reserpine in a dose-dependent manner. We conclude that CylAB closely resembles an ABC-type MDR transporter and propose that the GBS hemolysin molecule represents a natural substrate of the transporter.
Gottschalk
Birgit
B
Department of Medical Microbiology and Hygiene, University of Ulm, Robert Koch Str. 8, D-89081 Ulm, Germany.
Bröker
Gerd
G
Kuhn
Melanie
M
Aymanns
Simone
S
Gleich-Theurer
Ute
U
Spellerberg
Barbara
B
D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001433:Bacteriolysis; D001483:Base Sequence; D004317:Doxorubicin / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D006460:Hemolysin Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012110:Reserpine / Q000378:metabolism; D013292:Streptococcus agalactiae / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic
D000900:Anti-Bacterial Agents; D006460:Hemolysin Proteins; D026901:Membrane Transport Proteins; D004317:Doxorubicin; D012110:Reserpine