title: Evidence that pneumococcal WalK is regulated by StkP through protein-protein interaction.
abstract: WalRK is the only two-component regulatory system essential for viability in Streptococcus pneumoniae. Despite its importance, the biological role of this system is not well understood. However, previous studies have shown that it has a crucial role in controlling pneumococcal cell division. Considerable efforts have been made to understand how the WalRK system is regulated, but no signal(s) sensed by the WalK histidine kinase has been identified so far. Here, we provide evidence that the serine/threonine protein kinase StkP modulates the activity of WalK through direct protein-protein interaction, suggesting that this interaction is one of the signals sensed by WalK. In most low-G+C content Gram-positive bacteria, WalK orthologues are attached to the cytoplasmic membrane via two transmembrane segments separated by a large extracellular loop believed to function as a sensor domain. In contrast, members of the genus Streptococcus have WalK histidine kinases that are anchored to the cytoplasmic membrane by a single transmembrane segment. It has been a long-standing question whether this segment only serves as a membrane anchor or if it also functions as a signal-sensing domain. Our data strongly support the latter, i.e. that the transmembrane segment senses signals that regulate the activity of WalK.
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NO-1432 Ås, Norway.
authors.forename: Gro Anita
authors.initials: GA
authors.lastname: Stamsås
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NO-1432 Ås, Norway.
authors.forename: Daniel
authors.initials: D
authors.lastname: Straume
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NO-1432 Ås, Norway.
authors.forename: Zhian
authors.initials: Z
authors.lastname: Salehian
authors.affiliation: Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NO-1432 Ås, Norway.
authors.forename: Leiv Sigve
authors.initials: LS
authors.lastname: Håvarstein
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001482:Base Composition / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D000072417:Protein Domains / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013296:Streptococcus pneumoniae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C119939:YycF protein, Bacteria; D017346:Protein Serine-Threonine Kinases