MucE has the C-terminal –WVF motif that can activate this website the protease AlgW, thereby causing the degradation of the anti-sigma factor MucA. The degradation of MucA results in the release of AlgU to activate transcription at the P algU, P algD  and P mucE  promoter sites. Qiu et al. have reported that MucE can induce alginate overproduction when over-expressed in vivo[9]. However, nothing was known about the regulation of mucE. Recently, the genome-wide transcriptional start sites of many genes were mapped by RNA-seq in P. aeruginosa strain PA14 [28]. However, the transcriptional start site of the mucE gene (PA14_11670) was not included. In this study, we reported the mapping of the mucE transcriptional

start site. Furthermore, we found the transcription of selleck chemical mucE is dependent on AlgU. ABT263 Analysis of the upstream region of mucE reveals an AlgU promoter-like sequence (Figure 1). Previously, Firoved et al. identified 35 genes in the AlgU regulon, based on scanning for AlgU promoter consensus sequence (GAACTTN16-17TCtgA) in the PAO1 genome [26]. In this study, we found that AlgU can activate the transcription of mucE. In order

to determine whether AlgU can bind to P mucE region, AlgU was purified (Additional file 1: Figure S3) and electrophoretic mobility shift assay (EMSA) was performed. As seen in Additional file 1: Figure S4, our results showed that AlgU affected the mobility of P mucE DNA, especially in the presence of E. coli RNA polymerase core enzyme, suggesting a GBA3 direct binding of AlgU to P mucE . However, whether small regulatory RNAs or other unknown regulator proteins

are also involved in the transcriptional regulation of mucE needs further study. LptF is another example of an AlgU-dependent gene, but doesn’t have the consensus sequence in the promoter region [29]. While MucE, as a small envelope protein is positively regulated through a feedback mechanism, it’s not clear how many AlgU-regulated genes follow the same pattern of regulation as MucE. The mucA mutation is a major mechanism for the conversion to mucoidy. Mutation can occur throughout the mucA gene (585 bps) [30]. These mutations result in the generation of MucA proteins of different sizes. For example, unlike the wild type MucA with 194 amino acid residues, MucA25, which is produced due to a frameshift mutation, results in a protein containing the N-terminal 59 amino acids of MucA, fused with a stretch of 35 amino acids without homology to any known protein sequence [31]. MucA25 lacks the trans-membrane domain of wild type MucA, predicting a cytoplasmic localization. Therefore, different mucA mutations could possibly result in different cellular compartment localization. Identification of MucE’s function as an inducer of alginate in strains with wild type MucA and AlgU strongly suggests MucE acts through interaction with AlgW in the periplasm.