PMID:24659773

Citation	'Williams, ML, Crowley, PJ, Hasona, A and Brady, LJ (2014) YlxM is a Newly Identified Accessory Protein that Influences Function of Signal Recognition Particle (SRP) Pathway Components in Streptococcus mutans. J. Bacteriol. '
Abstract	Streptococcus mutans is a cariogenic oral pathogen whose virulence is determined largely by its membrane composition. The Signal Recognition Particle (SRP) protein-targeting pathway plays a pivotal role in membrane biogenesis. S. mutans SRP pathway mutants demonstrate growth defects, cannot contend with environmental stress, and exhibit multiple changes in membrane composition. This study sought to define a role for ylxM, which in S. mutans and numerous other bacteria resides directly upstream of the ffh gene encoding a major functional element of the bacterial SRP. YlxM was observed as a produced protein in S. mutans. Its predicted helix-turn-helix motif suggested a role as a transcriptional regulator of components within the SRP pathway, however, no evidence of transcriptional regulation was found. Instead, capture ELISA, affinity chromatography, and Biolayer Interferometry (BLI) demonstrated that S. mutans YlxM interacts with the SRP components Ffh and scRNA, but not with the SRP receptor FtsY. In the absence of FtsY, YlxM increased the GTP hydrolysis activity of Ffh alone and in complex with scRNA. However, in the presence of FtsY, YlxM caused an overall diminution of net GTPase activity. Thus, YlxM appears to modulate GTP hydrolysis, a process necessary for proper recycling of SRP pathway components. The presence of YlxM conferred a significant competitive growth advantage under non-stress and acid-stress conditions when wild-type and ylxM mutant strains were cultured together. Our results identify YlxM as a component of the S. mutans SRP and suggest a regulatory function affecting GTPase activity.
Links	PubMed Online version:10.1128/JB.01465-13
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STRMU:Y1061		GO:0030695: GTPase regulator activity	ECO:0000315:		F		Figure 4: An endpoint colorimetric assay indicated that the GTPase activity of Ffh alone, as well as that of Ffh/scRNA, was significantly increased upon addition of YlxM.	complete CACAO 9826
STRMU:Y1061	enables	GO:0030695: GTPase regulator activity	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete

References

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