Screening of Streptococcus pneumoniae ABC Transporter Mutants Demonstrates that LivJHMGF, a Branched-Chain Amino Acid ABC Transporter, Is Necessary for Disease Pathogenesis

TY - JOUR

T1 - Screening of Streptococcus pneumoniae ABC Transporter Mutants Demonstrates that LivJHMGF, a Branched-Chain Amino Acid ABC Transporter, Is Necessary for Disease Pathogenesis

AU - Basavanna, Shilpa

AU - Khandavilli, Suneeta

AU - Yuste, Jose

AU - Cohen, Jonathan M.

AU - Hosie, Arthur H. F.

AU - Webb, Alexander J.

AU - Thomas, Gavin H.

AU - Brown, Jeremy S.

PY - 2009/8

Y1 - 2009/8

N2 - Bacterial ABC transporters are an important class of transmembrane transporters that have a wide variety of substrates and are important for the virulence of several bacterial pathogens, including Streptococcus pneumoniae. However, many S. pneumoniae ABC transporters have yet to be investigated for their role in virulence. Using insertional duplication mutagenesis mutants, we investigated the effects on virulence and in vitro growth of disruption of 9 S. pneumoniae ABC transporters. Several were partially attenuated in virulence compared to the wild-type parental strain in mouse models of infection. For one ABC transporter, required for full virulence and termed LivJHMGF due to its similarity to branched-chain amino acid (BCAA) transporters, a deletion mutant (Delta livHMGF) was constructed to investigate its phenotype in more detail. When tested by competitive infection, the Delta livHMGF strain had reduced virulence in models of both pneumonia and septicemia but was fully virulent when tested using noncompetitive experiments. The Delta livHMGF strain had no detectable growth defect in defined or complete laboratory media. Recombinant LivJ, the substrate binding component of the LivJHMGF, was shown by both radioactive binding experiments and tryptophan fluorescence spectroscopy to specifically bind to leucine, isoleucine, and valine, confirming that the LivJHMGF substrates are BCAAs. These data demonstrate a previously unsuspected role for BCAA transport during infection for S. pneumoniae and provide more evidence that functioning ABC transporters are required for the full virulence of bacterial pathogens.

AB - Bacterial ABC transporters are an important class of transmembrane transporters that have a wide variety of substrates and are important for the virulence of several bacterial pathogens, including Streptococcus pneumoniae. However, many S. pneumoniae ABC transporters have yet to be investigated for their role in virulence. Using insertional duplication mutagenesis mutants, we investigated the effects on virulence and in vitro growth of disruption of 9 S. pneumoniae ABC transporters. Several were partially attenuated in virulence compared to the wild-type parental strain in mouse models of infection. For one ABC transporter, required for full virulence and termed LivJHMGF due to its similarity to branched-chain amino acid (BCAA) transporters, a deletion mutant (Delta livHMGF) was constructed to investigate its phenotype in more detail. When tested by competitive infection, the Delta livHMGF strain had reduced virulence in models of both pneumonia and septicemia but was fully virulent when tested using noncompetitive experiments. The Delta livHMGF strain had no detectable growth defect in defined or complete laboratory media. Recombinant LivJ, the substrate binding component of the LivJHMGF, was shown by both radioactive binding experiments and tryptophan fluorescence spectroscopy to specifically bind to leucine, isoleucine, and valine, confirming that the LivJHMGF substrates are BCAAs. These data demonstrate a previously unsuspected role for BCAA transport during infection for S. pneumoniae and provide more evidence that functioning ABC transporters are required for the full virulence of bacterial pathogens.

KW - SURFACE-ADHESIN-A

KW - BINDING CASSETTE SYSTEMS

KW - ESCHERICHIA-COLI

KW - VIRULENCE GENES

KW - MURINE MODEL

KW - IRON UPTAKE

KW - IN-VIVO

KW - PSAA

KW - IDENTIFICATION

KW - LIPOPROTEINS

UR - http://www.scopus.com/inward/record.url?scp=67651233743&partnerID=8YFLogxK

U2 - 10.1128/IAI.01543-08

DO - 10.1128/IAI.01543-08

M3 - Article

SN - 1098-5522

VL - 77

SP - 3412

EP - 3423

JO - Infection and Immunity

JF - Infection and Immunity

IS - 8

ER -