present the identification of StsC from Streptomyces somaliensis, a member of the UbiA
superfamily, as a membrane-bound sesterterpene cyclase in bacteria. The cyclized products
for StsC, somaliensenes A (1) and B (2), were identified by expressing the corresponding
gene in an engineered Escherichia coli strain. The structures of 1 and 2 were determined by
analysis of the NMR and MS spectroscopic data.