An ATP-dependent ligase with substrate flexibility involved in assembly of the peptidyl nucleoside antibiotic polyoxin

Authors: GONG, RONG - Wuhan University; QI, JIANZHAO - Wuhan University; WU, PAN - Wuhan University; CAI, YOU-SHENG - Wuhan University; MA, HONGMIN - Wuhan University; LIU, YANG - Wuhan University; DUAN, HE - Wuhan University; WANG, MENG - Wuhan University; DENG, ZIXIN - Wuhan University; Price, Neil; CHEN, WENQING - Wuhan University

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2018
Publication Date: 4/27/2018
Citation: Gong, R., Qi, J., Wu, P., Cai, Y., Ma, H., Liu, Y., Duan, H., Wang, M., Deng, Z., Price, N.P.J., Chen, W. 2018. An ATP-dependent ligase with substrate flexibility involved in assembly of the peptidyl nucleoside antibiotic polyoxin. Applied and Environmental Microbiology. doi: 10.1128/AEM.00501-18.
DOI: https://doi.org/10.1128/AEM.00501-18

Interpretive Summary: Polyoxin is a natural product, well known for its remarkable antifungal bioactivities and unusual structural features. Actually, elucidation of the polyoxin biosynthesis not only provides the enzymatic basis for further biosynthetic understanding of related peptidyl nucleoside antibiotics, but also contributes to the rational generation of more hybrid nucleoside antibiotics via synthetic biology strategy. New polyoxins are anticipated to find potential use as antifungal agents for agricultural purposes.

Technical Abstract: Polyoxin (POL) is an unusual nucleoside antibiotic, in which peptidyl moiety and nucleoside skeleton are linked by an amide bond. However, their biosynthesis remains poorly understood. Here, we report the deciphering of PolG as an ATP-dependent ligase responsible for the assembly of POL. A polG mutant is capable of accumulating multiple intermediates, including the peptidyl moiety (carbamoylpolyoxamic acid, CPOAA) and the nucleosides skeletons (POL-C and the previously overlooked thymine POL-C). We further demonstrated that PolG employs an ATP-dependent mechanism for amide bond formation, and that the generation of the hybrid nucleoside antibiotic, POL-N, is also governed by PolG. Finally, we determined that the deduced ATP-binding sites are functionally essential for PolG, and that they are highly conserved in a number of related ATP-dependent ligases. These insights have allowed us proposed a catalytic mechanism for the assembly of peptidyl nucleoside antibiotic via an acyl-phosphate intermediate, and have opened the way for the combinatorial biosynthesis/pathway engineering of this group of nucleoside antibiotics.