posted on 2023-01-06, 21:09authored byYaoyao Shen, Liu Zhang, Ming Yang, Ting Shi, Yongzhen Li, Lei Li, Yi Yu, Hai Deng, Hou-Wen Lin, Yongjun Zhou
Lavanduquinocin
(LDQ) is a potent neuroprotective carbazole alkaloid
from Streptomyces species that features a rare cyclic
monoterpene/cyclolavandulyl moiety attached to the tricyclic carbazole
nucleus. We elucidated the biosynthetic logic of LDQ by enzymatically
reconstituting the total biosynthetic pathway and identified the genes
required for generating the cyclolavandulyl moiety in LDQ based on
mutagenetic analysis, including a cyclolavandulyl diphosphate synthase
gene ldqA and a squalene synthase-like aromatic prenyltransferase
gene ldqG. LdqG is homologous to carbazole prenyltransferases,
NzsG and CqsB4, discovered from the biosynthetic pathways of two bacterial
carbazoles, neocarazostatin and carquinostatin. Based on analysis
of the sequences and modeled protein structures, further in vitro
and in vivo site-directed mutagenetic analyses led to identification
of two residue sites, F53 and C57 in NzsG vs I54 and A58 in LdqG,
which play crucial roles in governing the prenyl donor specificities
toward cyclolavandulyl, dimethylallyl, and geranyl diphosphates. By
applying this knowledge in strain engineering, prenyl donor delivery
was rationally switched to produce the desired prenylated carbazoles.
The study provides an opportunity to rationally manipulate the prenylation
modification to carbazole alkaloids, which could influence the biological
activities by increasing the affinity for membranes as well as the
interactions with cellular targets.