What is the fine-grained topic of the following text: In R. leguminosarum PTSNtr is a phosphotransferase system that globally regulates ATP-binding cassette (ABC) transport systems (Prell et al., 2012: Molecular Microbiology 84:117-129) and has been demonstrated to inactivate ABC transport under potassium limitation (Untiet et al. Only return the topic.
The regulation and inactivation of ATP-binding cassette transport systems in R. leguminosarum under potassium limitation.