Fragmentation study on butanolides with tandem mass spectrometry and its application for the screening of ScbR-captured quorum sensing molecules in Streptomyces coelicolor A3(2).

Streptomyces coelicolor has a quorum sensing (QS) system triggered by small diffusible signaling molecules, i.e. butanolides (or gamma-butyrolactones) and their cognate DNA-binding receptors. Using the DNA-binding receptors as an affinity capture matrix, the butanolides can be easily enriched and identified. For the identification and screening of the butanolides, the diagnostic peak lists generated by the tandem mass spectrometric (MS/MS) fragmentation analysis of chemically synthetic butanolides were used. In the case of using ScbR as the capture matrix, SCB1, a previously well-known butanolide, and Acl-1 (or SCB3)-type butanolides having one more carbon in the acyl chain than SCB1, were detected. This is the first report directly demonstrating that Acl-1 is able to bind to ScbR in S. coelicolor. Our proposed method using both diagnostic peak lists of butanolide and the purified receptor protein as an affinity capture tool can be applied to rapidly screen QS molecules in vitro.