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n-Alkylboronic Acid Inhibitors Reveal Determinants of Ligand Specificity in the Quorum-Quenching and Siderophore Biosynthetic Enzyme PvdQ
Structural highlights
FunctionPVDQ_PSEAE Catalyzes the deacylation of acyl-homoserine lactone (AHL or acyl-HSL), releasing homoserine lactone (HSL) and the corresponding fatty acid. Possesses a specificity for the degradation of long-chain acyl-HSLs (side chains of 11 to 14 carbons in length). Degrades 3-oxo-C12-HSL, one of the two main AHL signal molecules of P.aeruginosa, and thereby functions as a quorum quencher, inhibiting the las quorum-sensing system. Therefore, may enable P.aeruginosa to modulate its own quorum-sensing-dependent pathogenic potential. Also appears to be required for pyoverdin biosynthesis.[1] [2] [3] Publication Abstract from PubMedThe enzyme PvdQ (E.C. 3.5.1.97) from Pseudomonas aeruginosa is an N-terminal nucleophile hydrolase that catalyzes the removal of an N-myristyl substituent from a biosynthetic precursor of the iron-chelating siderophore pyoverdine. Inhibitors of pyoverdine biosynthesis are potential antibiotics since iron is essential for growth and scarce in most infections. PvdQ also catalyzes hydrolytic amide bond cleavage of selected N-acyl-l-homoserine lactone quorum-sensing signals used by some Gram-negative pathogens to coordinate the transcription of virulence factors. The resulting quorum-quenching activity of PvdQ has potential applications in antivirulence therapies. To inform both inhibitor design and enzyme engineering efforts, a series of n-alkylboronic acid inhibitors of PvdQ was characterized to reveal determinants of ligand selectivity. A simple homologation series results in compounds with Ki values that span from 4.7 mM to 190 pM, with a dependence of DeltaGbind values on chain length of -1.0 kcal/mol/CH2. X-ray crystal structures are determined for the PvdQ complexes with 1-ethyl-, 1-butyl-, 1-hexyl-, and 1-octylboronic acids at 1.6, 1.8, 2.0, and 2.1 A resolution, respectively. The 1-hexyl- and 1-octylboronic acids form tetrahedral adducts with the active-site N-terminal Ser217 in the beta-subunit of PvdQ, and the n-alkyl substituents are bound in the acyl-group binding site. The 1-ethyl- and 1-butylboronic acids also form adducts with Ser217 but instead form trigonal planar adducts and extend their n-alkyl substituents into an alternative binding site. These results are interpreted to propose a ligand discrimination model for PvdQ that informs the development of PvdQ-related tools and therapeutics. n-Alkylboronic Acid Inhibitors Reveal Determinants of Ligand Specificity in the Quorum-Quenching and Siderophore Biosynthetic Enzyme PvdQ.,Clevenger KD, Wu R, Liu D, Fast W Biochemistry. 2014 Oct 28;53(42):6679-86. doi: 10.1021/bi501086s. Epub 2014 Oct, 17. PMID:25290020[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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