UC Berkeley

Living systems are remarkably efficient in their ability to build complex molecular function, using a relatively small set of chemical functional groups to drive the wide range of life processes. In contrast, synthetic compounds access a much broader scope of structural and reaction diversity to tune desired chemical properties. However, unusual functional groups can be found in Nature. Many pathways for secondary metabolism produce compounds that could be useful for chemical applications if their biosynthesis could be repurposed. Here, we report the discovery and characterization of a unique pathway to produce a terminal alkyne-containing amino acid, β- ethynylserine, by the microbe Streptomyces cattleya through an unexpected reaction sequence that includes radical halogenation and oxidative C-C bond cleavage, followed by a desaturation that proceeds through a putative allene intermediate. We also report progress in porting the bes pathway into heterologous host, particularly E. coli. Furthermore, we present preliminary work on the discovery of a protein who’s function is to prevent translation of β-ethynylserine by acting as a tRNA proofreading enzyme. This pathway, and the auxiliary proteins related to control of translation of non-standard amino acids, offers the potential to genetically encode the de novo production of halo-, alkene-, and alkyne-labeled proteins and peptides from glucose to provide bioorthogonal functionality for downstream applications.