In:
Journal of Bacteriology, American Society for Microbiology, Vol. 197, No. 13 ( 2015-07-01), p. 2160-2170
Abstract:
The SpxA1 and SpxA2 (formerly SpxA and SpxB) transcriptional regulators of Streptococcus mutans are members of a highly conserved family of proteins found in Firmicutes , and they were previously shown to activate oxidative stress responses. In this study, we showed that SpxA1 exerts substantial positive regulatory influence over oxidative stress genes following exposure to H 2 O 2 , while SpxA2 appears to have a secondary regulatory role. In vitro transcription (IVT) assays using purified SpxA1 and/or SpxA2 showed that SpxA1 and, less often, SpxA2 directly activate transcription of some of the major oxidative stress genes. Addition of equimolar concentrations of SpxA1 and SpxA2 to the IVT reactions neither enhanced transcription of the tested genes nor disrupted the dominant role of SpxA1. Substitution of a conserved glycine residue (G52) present in both Spx proteins by arginine (Spx G52R ) resulted in strains that phenocopied the Δ spx strains. Moreover, addition of purified SpxA1 G52R completely failed to activate transcription of ahpC , sodA , and tpx , further confirming that the G52 residue is critical for Spx functionality. IMPORTANCE Streptococcus mutans is a pathogen associated with the formation of dental caries in humans. Within the oral cavity, S. mutans routinely encounters oxidative stress. Our previous data revealed that two regulatory proteins, SpxA1 and SpxA2 (formerly SpxA and SpxB), bear high homology to the Spx regulator that has been characterized as a critical activator of oxidative stress genes in Bacillus subtilis . In this report, we prove that Spx proteins of S. mutans directly activate transcription of genes involved in the oxidative stress response, though SpxA1 appears to have a more dominant role than SpxA2. Therefore, the Spx regulators play a critical role in the ability of S. mutans to thrive within the oral cavity.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2015
detail.hit.zdb_id:
1481988-0
SSG:
12
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