LepI is a novel multifunctional enzyme that catalyzes stereoselective dehydration, Diels-Alder reaction, and retro-Claisen rearrangement. Here we report the crystal structure of LepI in complex with its co-factor S-adenosyl methionine (SAM). LepI forms a tetramer via the N-terminal helical domain and binds to a SAM molecule in the C-terminal catalytic domain. The binding modes of various LepI substrates are investigated by docking simulations, which suggest that the substrates are bound via both hydrophobic and hydrophilic forces, as well as cation-π interactions with the positively charged SAM. The reaction starts with a dehydration step in which H133 possibly deprotonates the pyridone hydroxyl group of the substrate, while D296 might protonate an alkyl-chain hydroxyl group. Subsequent pericyclization may be facilitated by the correct fold of the substrate's alkyl chain and a thermodynamic driving force towards σ-bonds at the expense of π-bonds. These results provide structural insights into LepI catalysis and are important in understanding the mechanism of enzymatic pericyclization.
Bibliographical noteFunding Information:
This work has been supported by the Israel Science Foundation (grants # 2146/15 and 1683/18); the National Natural Science Foundation of China (grants 31870790, 31470240 and 31570130); KFZD-SW-215-01 from Chinese Academy of Sciences (CAS); CAS Interdisciplinary Innovation Team; Youth Innovation Promotion Association, CAS; Taiwan Young Visiting Scholar Funding, CAS; China National Tobacco Corporation, (grant 110201502018, 110201502014 and 027Y2014-013); and the Taiwan Protein Project (grant no. AS-KPQ-105-TPP). The synchrotron data collection was conducted at beam lines TPS-05A, BL13C1 and BL15A1 of NSRRC (National Synchrotron Radiation Research Center, Taiwan).
© The Royal Society of Chemistry.