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.
GSK Biologicals, Rixensart, Belgium.
Stéphane
S
Rioux
GSK Biologicals, Rixensart, Belgium.
Cécile
C
Neyt
GSK Biologicals, Rixensart, Belgium.
Emmanuel
E
Di Paolo
GSK Biologicals, Rixensart, Belgium.
Laurence
L
Turpin
Medicago Inc., Québec, Québec, Canada.
Nathalie
N
Charland
GSK Biologicals, Laval, Québec, Canada.
Steve
S
Labbé
GSK Biologicals, Rixensart, Belgium.
Marie-Cécile
MC
Mortier
University of Glasgow, Glasgow, UK.
Tim J
TJ
Mitchell
GSK Biologicals, Rixensart, Belgium.
Christiane
C
Feron
GSK Biologicals, Laval, Québec, Canada.
Denis
D
Martin
GSK Biologicals, Rixensart, Belgium.
Jan T
JT
Poolman
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