Positive control of the two‐component RcsC/B signal transduction network by DjlA: a member of the DnaJ family of molecular chaperones in Escherichia coli

Abstract

SummaryThe membrane-anchored DjlA protein represents the third member of the DnaJ 'J-domain' family of Escherichia coli that includes DnaJ and CbpA. DjlA possesses a J-domain at its extreme C-terminus but shares no additional homology with DnaJ. Our genetic analysis suggests that DjlA acts in concert with the RcsB/C two-component signal transduction system to augment induction of the cps (capsular polysaccharide) operon and synthesis of colanic acid mucoid capsule. The DjlA J-domain is essential for the observed stimulation of this pathway as deletion, or introduction of the mutation H233Q, within the highly conserved HPD tripeptide abolished all inducing activity. Deletion of the transmembrane anchor sequence also abolished all inducing activity. djlA is not an essential gene under all conditions tested, nor is it essential for mucoid capsule biosynthesis; however, strong overexpression leads to rapid loss of cell viability suggesting that the gene is normally tightly regulated. Northern analysis revealed that djlA message was extremely unstable but could be induced or stabilized in response to cold shock. The activation of the cps operon by DjlA is dependent upon both DnaK(Hsp70) and GrpE, and therefore we propose a role for DjlA, together with this chaperone machine, as a novel regulator of a two-component histidine kinase signal transduction pathway.

n-Hexane sensitivity of Escherichia coli due to low expression of imp/ostA encoding an 87 kDa minor protein associated with the outer membrane

“…The IS5 insertion divided djlA into two parts within the 26th codon and destroyed the N-terminal transmembrane domain of the product DjlA, suggesting that djlA was not functional in OST4251. DjlA belongs to the DnaJ family of molecular chaperones (Kelley & Georgopoulos, 1997). Overexpression of djlA prompts capsule synthesis (Clarke et al, 1996).…”

The importance of the Rcs phosphorelay in the survival and pathogenesis of the enteropathogenic yersiniae

“…Capsular polysaccharide expression and major cell envelope modifications appear to be a common theme of Rcs phosphorelay activation and it has been also proposed to play a role in regulating bacterial virulence and biofilm formation (Arricau et al, 1998;Ferrières & Clarke, 2003;Francez-Charlot et al, 2005;Tobe et al, 2005;Vianney et al, 2005). As yet the precise signal for pathway activation has not been determined, but it appears that the RcsC sensor responds to membrane perturbations such as osmotic stress, desiccation, bile salts and the aberrant expression of certain membrane-associated proteins (Ophir & Gutnick, 1994;Sledjeski & Gottesman, 1996;Clarke et al, 1997;Bernstein et al, 1999;Kelley & Georgopoulos, 1997;Potrykus & Wegrzyn, 2004;Zuber et al, 1995). Activation of this pathway has also been shown to occur during growth on a solid medium (Ferrières & Clarke, 2003).…”

Virulence attenuation in Salmonella enterica rcsC mutants with constitutive activation of the Rcs system

“…Furthermore, several genetic conditions that result in alterations in envelope composition or integrity are known to activate the Rcs system. For example, a mutation in the mdoH gene involved in the biosynthesis of membrane-derived oligosaccharides (Ebel et al, 1997) or overproduction of the DnaJ-like transmembrane protein DjlA (Kelley & Georgopoulos, 1997) has been shown to stimulate the expression of genes regulated by the E. coli Rcs system. In Salmonella enterica serovar Typhimurium, mutations in the essential gene igaA (Cano et al, 2001) [also known as yrfF or mucM (Costa & Antó n, 2001)] result in mucoidy and reduced motility (Cano et al, 2002).…”