Polymorphism and regulation of the spxB (pyruvate oxidase) virulence factor gene by a CBS-HotDog domain protein (SpxR) in serotype 2 Streptococcus pneumoniae.
spxB-encoded pyruvate oxidase is a major virulence factor of Streptococcus pneumoniae. During aerobic growth, SpxB synthesizes H2O2 and acetyl phosphate, which play roles in metabolism, signalling, and oxidative stress. We report here the first cis- and trans-acting regulatory elements for spxB transcription. These elements were identified in a genetic screen for spontaneous mutations that caused colonies of strain D39 to change from a semitransparent to an opaque appearance. Six of the seven opaque colonies recovered (frequency approximately 3 x 10(-5)) were impaired for SpxB function or expression. Two mutations changed amino acids in SpxB likely required for cofactor or subunit binding. One mutation defined a cis-acting adjacent direct repeat required for optimal spxB transcription. The other three spontaneous mutations created the same frameshift near the start of the trans-acting spxR regulatory gene. The SpxR protein contains helix-turn-helix, CBS and HotDog domains implicated in binding DNA, adenosyl compounds, and CoA-containing compounds respectively, and suggest that SpxR positively regulates spxB transcription in response to energy and metabolic state. Microarray analyses unexpectedly demonstrated that SpxR also positively regulates the strH exoglycosidase gene, which, like spxB, has been implicated in colonization. Finally, SpxR is required for full virulence in a murine model of infection.
Ramos-Montañez
Smirla
S
Department of Biology, Indiana University Bloomington, Bloomington, IN 47405, USA.
Tsui
Ho-Ching Tiffany
HC
Wayne
Kyle J
KJ
Morris
Jordan L
JL
Peters
Lindsey E
LE
Zhang
Faming
F
Kazmierczak
Krystyna M
KM
Sham
Lok-To
LT
Winkler
Malcolm E
ME
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011008:Pneumococcal Infections / Q000382:microbiology*; D011110:Polymorphism, Genetic; D011771:Pyruvate Oxidase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D037521:Virulence Factors; D011771:Pyruvate Oxidase