Transcriptional regulation, occurrence and putative role of the Pht family of Streptococcus pneumoniae.
Restricted to the genus Streptococcus, the Pht protein family comprises four members: PhtA, PhtB, PhtD and PhtE. This family has the potential to provide a protein candidate for incorporation in pneumococcal vaccines. Based on sequence analysis and on RT-PCR experiments, we show here that the pht genes are organized in tandem but that their expression, except that of phtD, is monocistronic. PhtD, PhtE, PhtB and PhtA are present in 100, 97, 81 and 62 % of the strains, respectively, and, by analysing its sequence conservation across 107 pneumococcal strains, we showed that PhtD displays very little variability. To analyse the physiological function of these proteins, several mutants were constructed. The quadruple Pht-deficient mutant was not able to grow in a poor culture medium, but the addition of Zn(2+) or Mn(2+) restored its growth capacity. Moreover, the phtD mRNA expression level increased when the culture medium was depleted in zinc. Therefore, we suggest that these proteins are zinc and manganese scavengers, and are able to store these metals and to release them when the bacterium faces an ion-restricted environment. The data also showed that this protein family, and more particularly PhtD, is a promising candidate to be incorporated into pneumococcal vaccines.
Rioux
Stéphane
S
GSK Biologicals, Rixensart, Belgium.
Neyt
Cécile
C
GSK Biologicals, Rixensart, Belgium.
Di Paolo
Emmanuel
E
GSK Biologicals, Rixensart, Belgium.
Turpin
Laurence
L
GSK Biologicals, Rixensart, Belgium.
Charland
Nathalie
N
Medicago Inc., Québec, Québec, Canada.
Labbé
Steve
S
GSK Biologicals, Laval, Québec, Canada.
Mortier
Marie-Cécile
MC
GSK Biologicals, Rixensart, Belgium.
Mitchell
Tim J
TJ
University of Glasgow, Glasgow, UK.
Feron
Christiane
C
GSK Biologicals, Rixensart, Belgium.
Martin
Denis
D
GSK Biologicals, Laval, Québec, Canada.
Poolman
Jan T
JT
GSK Biologicals, Rixensart, Belgium.
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008345:Manganese / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D011401:Promoter Regions, Genetic; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000254:growth & development; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic; D015032:Zinc / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008345:Manganese; D015032:Zinc