High-levels of 1,6-anhMurNAc-tripeptide accumulate in the absence of ampD. AmpD is an amidase that cleaves 1,6-anhMurNAc-tripeptide [13]. Induction of E. cloacae ampC was also shown to be ampG-dependent [14]. β-lactamase fusion analysis suggests MK-0457 cell line that E. coli AmpG contains 10 transmembrane segments and two large cytoplasmic loops [15]. E. coli AmpG was shown to transport N-acetylglucosamine-anhydrous

N-acetylmuramic acid (GlcNAc-anhMurNAc) and GlcNAc-anhMurNAc-tri, -tetra, and -pentapeptides [16, 17]. Comprehensive and elegant studies using Enterobacteriaceae established the paradigm of the β-lactamase induction mechanism. Orthologs of ampR, ampD, and ampG are found in numerous Gram-negative species [18]. Whether similar mechanisms are employed in all these organisms has not

been established. It is possible selleck chemical that the induction mechanism could differ. The β-lactamase induction mechanism of P. aeruginosa has not been well-defined; however, it is known that P. aeruginosa AmpR regulates expression of ampC as in other organisms [8–10]. Similar to other systems, ampR is located upstream of the ampC gene [10]. Additionally, P. aeruginosa AmpR controls transcription of the oxacillinase, poxB, and several genes involved in LCL161 chemical structure virulence [8–10]. Loss of AmpR in P. aeruginosa causes a significant elevation in β-lactamase activity and other virulence factors [10]. P. aeruginosa also differs from other previously studied systems in that its genome has two ampG orthologs, PA4218 and PA4393 [19]. The current study reveals that these two genes, PA4218 and PA4393, are required for β-lactamase induction, hence they have been named ampP Dipeptidyl peptidase and ampG, respectively. Consistent with their putative roles as permeases, fusion analysis suggests that AmpG and AmpP have 14 and 10 transmembrane helices, respectively. Expression of ampP is dependent upon AmpR and is autoregulated. Together, these data suggest the distinctiveness of P. aeruginosa β-lactamase induction, as it is the first system that potentially involves two permease paralogs,

and contribute to the general understanding of the induction mechanism. Results Genome Sequence Analysis of the PA4218 and PA4393 Operons E. coli AmpG has been shown to be a permease that transports GlcNAc-anhMurNAc peptides from the periplasm to the cytoplasm [13, 17]; however, the AmpG function in P. aeruginosa has not been described. BLAST analysis of the E. coli AmpG sequence against the six-frame translation of the PAO1 genome identified two open reading frames, PA4218 and PA4393, with significant homology [20, 21]. Global alignment using the Needleman-Wusch algorithm [22] demonstrated that PA4218 is 21.8% identical and 34.8% similar, while PA4393 is 23.2% identical and 34.3% similar to AmpG (Figure 1). The Pseudomonas Genome Database identifies PA4393 as encoding a putative permease with an alternate name of ampG, while PA4218 is identified as encoding a probable transporter [23].