Bifunctional quorum-quenching and antibiotic-acylase MacQ forms a 170-kDa capsule-shaped molecule containing spacer polypeptides

Abstract

Understanding the molecular mechanisms of bacterial antibiotic resistance will help prepare against further emergence of multi-drug resistant strains. MacQ is an enzyme responsible for the multi-drug resistance of Acidovorax sp. strain MR-S7. MacQ has acylase activity against both N-acylhomoserine lactones (AHLs), a class of signalling compounds involved in quorum sensing, and β-lactam antibiotics. Thus, MacQ is crucial as a quencher of quorum sensing as well as in conferring antibiotic resistance in Acidovorax. Here, we report the X-ray structures of MacQ in ligand-free and reaction product complexes. MacQ forms a 170-kDa capsule-shaped molecule via face-to-face interaction with two heterodimers consisting of an α-chain and a β-chain, generated by the self-cleaving activity of a precursor polypeptide. The electron density of the spacer polypeptide in the hollow of the molecule revealed the close orientation of the peptide-bond atoms of Val20SP-Gly21SP to the active-site, implying a role of the residues in substrate binding. In mutational analyses, uncleaved MacQ retained degradation activity against both AHLs and penicillin G. These results provide novel insights into the mechanism of self-cleaving maturation and enzymatic function of N-terminal nucleophile hydrolases.

Novel N-Acyl Homoserine Lactone-Degrading Bacteria Isolated From Penicillin-Contaminated Environments and Their Quorum-Quenching Activities

“…Besides, our group and other two research groups reported that AHL-acylases (MacQ, AhlM, and KcPGA) could function as β-lactam acylase, and indeed degrade PENG via hydrolysis of the amide bond ( Park et al, 2005 ; Mukherji et al, 2014 ; Kusada et al, 2017 ). Furthermore, we recently solved the X-ray crystal structure of MacQ, and found that the degradation products of C 10 -HSL and PENG by MacQ were commonly accommodated in the same hydrophobic active-site pocket, indicating that both compounds were hydrolyzed by MacQ in the same degradation mechanism ( Yasutake et al, 2017 ). Perhaps, some AHL-acylases (β-lactam acylases) may have broad substrate specificity that appears to be structurally indistinguishable from both AHL-signals and β-lactam antibiotics.…”

Penicillin Acylase from Streptomyces lavendulae and Aculeacin A Acylase from Actinoplanes utahensis: Two Versatile Enzymes as Useful Tools for Quorum Quenching Processes

“…The model protein of subfamily 5C9IA is the aforementioned MacQ, an AHL acylase from Acidovorax sp. MR-S7, active towards both AHLs and β-lactam antibiotics [47]. In addition, a phylogenetic study was performed using MEGA X based on the amino acid sequences of 31 Ntn-hydrolases with reported amidase activities (Figure 4).…”

The Komagataeibacter europaeus GqqA is the prototype of a novel bifunctional N-Acyl-homoserine lactone acylase with prephenate dehydratase activity

“…Within this framework, it is notably, that the recently uncovered acylase MacQ has been described to be involved in QQ and antibiotic resistance. Thereby, MacQ acts against AHLs and Penicillin G and is an acylase belonging to the Ntn family 21 .…”