Feature-Based Molecular Networking for the Targeted Identification of G-Inhibiting FR900359 Derivatives.

Both the soil bacterium and the bacterial endosymbiont Burkholderia crenata of the plant are producers of FR900359 (FR). This cyclic depsipeptide is a potent and selective G protein inhibitor used extensively to investigate the intracellular signaling of G protein coupled receptors (GPCRs). In this study, the metabolomes of both FR producers were investigated and compared using feature-based molecular networking (FBMN). As a result, 30 previously unknown FR derivatives were identified, one-third being unique to . Guided by MS, a novel FR derivative, FR-6 (compound ), was isolated, and its structure unambiguously established. In a whole-cell biosensing assay based on detection of dynamic mass redistribution (DMR) as readout for G inhibition, FR-6 suppressed G signaling with micromolar potency (pIC = 5.56). This functional activity was confirmed in radioligand binding assays (p = 7.50). This work demonstrates the power of molecular networking, guiding the way to a novel G-inhibiting FR derivative and underlining the potency of FR as a G inhibitor.