Infect Immun. 2014 Jul 28. pii: IAI.02155-14. [Epub ahead of print]
Overlapping Functionality of the Pht Proteins in Zinc Homeostasis of Streptococcus pneumoniae.
Plumptre CD1, Hughes CE1, Harvey RM1, Eijkelkamp BA1, McDevitt CA1, Paton JC2.
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Abstract
Streptococcus pneumoniae is a globally significant pathogen that causes a range of diseases including pneumonia, sepsis, meningitis and otitis media. Its ability to do so depends upon the acquisition of nutrients from its environment, including transition metal ions such as zinc. The pneumococcus employs a number of surface proteins to achieve this, amongst which are four highly similar polyhistidine triad (Pht) proteins. It has previously been established that these proteins collectively aid in the delivery of zinc to the ABC transporter substrate binding protein AdcAII. Here we have investigated the contributions of each individual Pht protein to pneumococcal zinc homeostasis by analyzing mutant strains expressing only one of the four pht genes. Under conditions of low zinc availability, each of these mutants showed superior growth and zinc accumulation profiles relative to a mutant strain lacking all four genes, indicating that any of the four Pht proteins are able to facilitate delivery of zinc to AdcAII. However, optimal growth and zinc accumulation in vitro and pneumococcal survival and proliferation in vivo required production of all four Pht proteins, indicating that, despite their overlapping functionality, the proteins are not dispensable without incurring a fitness cost. We also show that surface attached forms of the Pht proteins are required for zinc recruitment, and that they do not contribute to defence against extracellular zinc stress.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
PMID: 25069983 [PubMed - as supplied by publisher]
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