Ecs, an ABC transporter of Bacillus subtilis: dual signal transduction functions affecting expression of secreted proteins as well as their secretion

Abstract

Summaryecs is a three-cistron operon of Bacillus subtilis, encoding proteins with similarity to the ATPase (EcsA) and hydrophobic components (EcsB) of ABC transporters. The ecsA26 point mutation was shown to cause a strong processing defect of a secreted ␣-amylase precursor (preAmyQ) and of three other exoproteins. Northern analysis of the level of amyQ mRNA showed that ecsA26 also decreases amyQ transcription. This effect too was pleiotropic, as judged by a drastic decrease in the expression from an exoprotease promoter of a reporter protein. A knockout mutation of the ecsB cistron caused a processing defect similar to ecsA26 but, unlike ecsA26, did not affect amyQ transcription. There was also no defect in transcription in the ecsA ecsB double mutant. Thus, an intact ecsB product was required for the downregulation of amyQ by the mutant ecsA. These results suggest a dual regulatory function for Ecs, in which Ecs, possibly as part of a signal transduction mechanism, regulates some component(s) of the protein secretion apparatus as well as secretory protein transcription in a co-ordinated fashion.

The Bacillus subtilis ABC transporter EcsAB influences intramembrane proteolysis through RasP

“…In pulse-chase experiments it became obvious that almost no processing of preAmyQ to its mature form took place when rasP was deleted (Fig. 4b), as has been described for the ecsA26 mutant strain (Leskela et al, 1999). Next, the transformation efficiency of the respective strains was determined.…”

“…Pulse-chase experiments were performed as described elsewhere (Leskela et al, 1999) using strain IH6531 and derivatives thereof obtained by transformation of chromosomal DNA of knockouts of ecsA (1012 ecsA : : spec), rasP (1012 rasP : : tet) and sigW (sigW : : erm of HB4246; Huang et al, 1998). Competence was analysed as the transformation efficiency (Kontinen & Sarvas, 1988), and the sporulation frequency according to a standard procedure (Nicholson & Setlow, 1990) using strain IH8209 and respective knockouts (see above).…”

“…First, that RasP activity itself is directly or indirectly dependent on EcsAB. For example, EcsAB is known to influence correct localization of secretory proteins (Leskela et al, 1999), and therefore could be involved in correct membrane insertion of RasP. Second, that an EcsAB substrate mislocated in the absence of the ABC transporter activity inhibits RasP.…”

“…Further characterization of this mutation revealed a pleiotropic phenotype. The mutant is impaired in processing of pre-AmyQ and three other secretory proteins, and its ability to sporulate and to become competent is decreased (Leskela et al, 1999;Pummi et al, 2002). In addition, a mutant for ecsB has been described that is unable to produce a biofilm (Branda et al, 2004).…”

Genetic and functional characterization of dpp genes encoding a dipeptide transport system in Lactococcus lactis

“…ABC transporters may have a role not only in nutrient accumulation, but also in other cellular processes (Lazazzera et al 1998). Regulation of gene expression is achieved when the translocated solute serves as a signaling molecule that interacts with an intracellular receptor, or when the transporter transduces a signal across the cytoplasmic membrane upon ligand binding (Leskelä et al 1999). The role of peptide transport systems in functions other than nutrition is exemplified by the oligopeptide permease (Opp) of Bacillus subtilis, which is involved in competence development and sporulation (Perego et al 1991;Rudner et al 1991), or the dipeptide permease (Dpp) of Escherichia coli, which is involved in chemotaxis (Abouhamad et al 1991;Manson et al 1986).…”