RESUMEN
The Rcs phosphorelay signal transduction system of Escherichia coli controls genes for capsule production and many other envelope-related functions and is implicated in biofilm formation. The outer-membrane lipoprotein RcsF is an essential component of the Rcs system. Mislocalization of RcsF to the periplasm or the cytoplasmic membrane leads to high activation of the Rcs system, suggesting that RcsF functions by interacting with the cytoplasmic membrane component(s) of the system in activating the system. This is consistent with the result reported by Cho et al. (Cell159, 1652-1664, 2014) showing that RcsF interacts with the periplasmic domain (YrfFperi) of the inner-membrane protein YrfF (IgaA in Salmonella enterica serovar Typhimurium), which is a negative regulator of the Rcs system. In this study we show that RcsF also interacts with the periplasmic domain of the innermembrane-localized histidine kinase RcsC (RcsCperi). RcsCperi, which was secreted to the periplasm by fusion to maltose-binding protein, titrated RcsF's activating effect. A bimolecular fluorescence complementation experiment showed interaction of RcsF with RcsCperi, as well as with YrfFperi. We conclude that RcsF interacts with the periplasmically exposed region of RcsC, as well as with that of YrfF.
Asunto(s)
Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Histidina Quinasa/metabolismo , Lipoproteínas/metabolismo , Complejos Multienzimáticos/metabolismo , Fosfoproteínas Fosfatasas/metabolismo , Proteínas Quinasas/metabolismo , Transducción de Señal , Escherichia coli/enzimología , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Histidina Quinasa/genética , Lipoproteínas/genética , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Complejos Multienzimáticos/genética , Fosfoproteínas Fosfatasas/genética , Unión Proteica , Proteínas Quinasas/genéticaRESUMEN
The outer membrane lipoprotein RcsF is an essential component of the Rcs phosphorelay signal transduction system in Escherichia coli. It senses stresses imposed on the cell envelope and conveys the information to histidine kinase RcsC in the cytoplasmic membrane. Mislocalization of RcsF to the periplasm, effected by fusing it to the periplasmic maltose-binding protein, or to the cytoplasmic membrane, brought about by changing the lipoprotein sorting signal, leads to high activation of the Rcs system, suggesting that RcsF functions as a ligand for RcsC in activating the system. Here, we focus on the proline-rich region (PRR) in the N-terminal half of RcsF, a region which also contains many basic amino acid residues. Deletion of the PRR in the mislocalized RcsF resulted in even higher activation of the Rcs system. The same deletion in wild-type RcsF lipoprotein that is correctly localized to the outer membrane, however, blocked activation of the system under stresses that normally should activate it. It is highly likely that the PRR plays an important role in the regulation of the function of RcsF in activating the Rcs system.