This Current Topic An impressive accumulation of work from several EFI cores and projects, this publication showcases the EFI's new focus on mining transporter-containing gene clusters for novel metabolic pathways. This technique represents a dramatic shift away from restricting discovery to specifc enzyme superfamilies. When targeted via the ligand/metabolite screening platform discussed here, transporters have been extremely fruitful at providing the starting point for downstream pathway discovery.
The rate at which genome sequencing data is accruing demands enhanced methods for functional annotation and metabolism discovery. Solute binding proteins (SBPs) facilitate the transport of the first reactant in a metabolic pathway, thereby constraining the regions of chemical space and the chemistries that must be considered for pathway reconstruction. We describe high-throughput protein production and differential scanning fluorimetry platforms, which enabled the screening of 158 SBPs against a 189 component library specifically tailored for this class of proteins. Like all screening efforts, this approach is limited by the practical constraints imposed by construction of the library, i.e., we can study only those metabolites that are known to exist and which can be made in sufficient quantities for experimentation. To move beyond these inherent limitations, we illustrate the promise of crystallographic- and mass spectrometric-based approaches for the unbiased use of entire metabolomes as screening libraries. Together, our approaches identified 40 new SBP ligands, generated experiment-based annotations for 2084 SBPs in 71 isofunctional clusters, and defined numerous metabolic pathways, including novel catabolic pathways for the utilization of ethanolamine as sole nitrogen source and the use of d-Ala-d-Ala as sole carbon source. These efforts begin to define an integrated strategy for realizing the full value of amassing genome sequence data.
Reprinted with permission from Vetting et al. Biochemistry 54, Epub ahead of print. Copyright 2014 American Chemical Society.