Small-molecule inhibitor binding to an N-acyl-homoserine lactone synthase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 29; pp. 12089 - 12094
• Main Authors: Chung, Jiwoung, Goo, Eunhye, Yu, Sangheon, Choi, Okhee, Lee, Jeehyun, Kim, Jinwoo, Kim, Hongsup, Igarashi, Jun, Suga, Hiroaki, Moon, Jae Sun, Hwang, Ingyu, Rhee, Sangkee
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 19-07-2011; National Acad Sciences
• Subjects: 4-Butyrolactone - analogs & derivatives; 4-Butyrolactone - metabolism; antagonists; Bacteria; Bacterial Proteins - antagonists & inhibitors; Bacterial Proteins - metabolism; Binding sites; Biological Sciences; Burkholderia - metabolism; Burkholderia glumae; Chemical reactions; Crystal structure; Crystallography, X-Ray; Enzymes; Fluorescence; Gram-negative bacteria; Homoserine - analogs & derivatives; Homoserine - metabolism; Hydrogen bonds; Lactones; Lactones - metabolism; ligands; Molecules; pathogens; population density; Protein Binding; protein secretion; Proteins; Quorum sensing; Quorum Sensing - physiology; Receptors; Research universities; S-adenosylmethionine; S-Adenosylmethionine - metabolism; Substrate Specificity; Transcription Factors - antagonists & inhibitors; Transcription Factors - metabolism; virulence; X-ray diffraction
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1103165108

Quorum sensing (QS) controls certain behaviors of bacteria in response to population density. In Gram-negative bacteria, QS is often mediated by N-acyl-L-homoserine lactones (acyl-HSLs). Because QS influences the virulence of many pathogenic bacteria, synthetic inhibitors of acyl-HSL synthases might be useful therapeutically for controlling pathogens. However, rational design of a potent QS antagonist has been thwarted by the lack of information concerning the binding interactions between acyl-HSL synthases and their ligands. In the Gram-negative bacterium Burkholderia glumae, QS controls virulence, motility, and protein secretion and is mediated by the binding of N-octanoyl-L-HSL (C8-HSL) to its cognate receptor, TofR. C8-HSL is synthesized by the acyl-HSL synthase TofI. In this study, we characterized two previously unknown QS inhibitors identified in a focused library of acyl-HSL analogs. Our functional and X-ray crystal structure analyses show that the first inhibitor, J8-C8, binds to TofI, occupying the binding site for the acyl chain of the TofI cognate substrate, acylated acyl-carrier protein. Moreover, the reaction byproduct, 5'-methylthioadenosine, independently binds to the binding site for a second substrate, S-adenosyl-L-methionine. Closer inspection of the mode of J8-C8 binding to TofI provides a likely molecular basis for the various substrate specificities of acyl-HSL synthases. The second inhibitor, E9C-3oxoC6, competitively inhibits C8-HSL binding to TofR. Our analysis of the binding of an inhibitor and a reaction byproduct to an acyl-HSL synthase may facilitate the design of a new class of QS-inhibiting therapeutic agents.