Long-Chain N -Acyl Amino Acid Synthases Are Linked to the Putative PEP-CTERM/Exosortase Protein-Sorting System in Gram-Negative Bacteria

Abstract

Clones that encode the biosynthesis of long-chain N-acyl amino acids are frequently recovered from activitybased screens of soil metagenomic libraries. Members of a diverse set of enzymes referred to as N-acyl amino acid synthases are responsible for the production of all metagenome-derived N-acyl amino acids characterized to date. Based on the frequency at which N-acyl amino acid synthase genes have been identified from metagenomic samples, related genes are expected to be common throughout the global bacterial metagenome. Homologs of metagenome-derived N-acyl amino acid synthase genes are scarce, however, within the sequenced genomes of cultured bacterial species. Toward the goal of understanding the role(s) played by N-acyl amino acids in environmental bacteria, we looked for conserved genetic features that are positionally linked to metagenome-derived N-acyl amino acid synthase genes. This analysis revealed that N-acyl amino acid synthase genes are frequently found adjacent to genes predicted to encode PEP-CTERM motif-containing proteins and, in some cases, other conserved elements of the PEP-CTERM/exosortase system. Although relatively little is known about the PEP-CTERM/exosortase system, its core components are believed to represent the putative Gram-negative equivalent of the LPXTG/sortase protein-sorting system of Gram-positive bacteria. During the course of this investigation, we were able to provide evidence that an uncharacterized family of hypothetical acyltransferases, which had previously been linked to the PEP-CTERM/exosortase system by bioinformatics, is a new family of N-acyl amino acid synthases that is widely distributed among the PEP-CTERM/exosortase system-containing Proteobacteria.

Both widespread PEP‐CTERM proteins and exopolysaccharides are required for floc formation of Zoogloea resiniphila and other activated sludge bacteria

“…The phosphorylated PrsR (PrsR∼P) is activated and binds to a well conserved enhancer upstream of RpoN recognizing promoter. The bound phosphorylated PrsR polymer flips over to interact with σ 54 and activates the σ 54 ‐RNA polymerase holoenzyme (Eσ 54 ) in an ATP‐dependent process leading to transcription of downstream PEP‐CTERM gene(s) (Craig et al ., ). The PEP‐CTERM proteins are secreted into the periplasm and anchored to the cytoplasmic membrane by their PEP‐CTERM motifs.…”

“…S10). The gene products are probably acidic proteins of similar sizes (212-359 residues) and contain an abundance of residues that potentially could be used for O-linked and N-linked glycosylation at Ser/ Thr and/or Asn residue respectively (Craig et al, 2011). Asparagine (Asn or N) is overrepresented in the PepA polypeptide and 8 of the 18 N are part of the Nx[ST] motif for N-linked glycosylation in eukaryotes (Mononen and Karjalainen, 1984).…”

In silico analyses of conservational, functional and phylogenetic distribution of the LuxI and LuxR homologs in Gram-positive bacteria

“…The domains from LuxI containing protein of Gram-positive bacteria are related to autoinducer synthesis. For example, “ Autoinducer synthase ” (IPR001690, IPR018311) responsible for synthesizing AHLs by utilizing acyl-(acyl-carrier proteins) (acyl-ACP) and amino acids as substrates in the presence of acyl transferase (IPR016181, Acetyltransf_5) 37 . Likewise, among LuxR containing proteins i.e.…”

“…Functional annotation of potential LuxI/LuxR incorporating proteins was accomplished using GO and ligand-based analysis. As LuxI containing proteins was assigned with “ transferase activity ”, which might helps Gram-positive bacteria to transfer acyl group during AHL synthesis 37 , 40 . In case of LuxR, predominant biological processes involve in DNA dependent and gene-specific transcription.…”

Archaeosortases and Exosortases Are Widely Distributed Systems Linking Membrane Transit with Posttranslational Modification

“…While this work was under review, Craig et al (10) reported that a previously uncharacterized family of acyltransferases regularly found in bacteria in gene neighborhoods shared with exosortases attach long-chain acyl groups to free amino acids. Because acyltransferase activity was characterized in heterologous systems possessing neither exosortase nor its putative PEP-CTERM targets, this work leaves open the possibility that these acyltransferases are involved primarily in PEP-CTERM protein modification, rather than in the production of a bioactive small molecule, as the article suggests, or in the modification of extracellular polysaccharides.…”