Journal: J Struct Biol / Year: 2019 Title: Cryo-electron microscopy structures of ArnA, a key enzyme for polymyxin resistance, revealed unexpected oligomerizations and domain movements. Authors: Meng Yang / Yu Seby Chen / Muneyoshi Ichikawa / Daniel Calles-Garcia / Kaustuv Basu / Rayan Fakih / Khanh Huy Bui / Kalle Gehring / Abstract: Gram-negative bacteria evade the attack of cationic antimicrobial peptides through modifying their lipid A structure in their outer membranes with 4-amino-4-deoxy-L-arabinose (Ara4N). ArnA is a ...Gram-negative bacteria evade the attack of cationic antimicrobial peptides through modifying their lipid A structure in their outer membranes with 4-amino-4-deoxy-L-arabinose (Ara4N). ArnA is a crucial enzyme in the lipid A modification pathway and its deletion abolishes the polymyxin resistance of gram-negative bacteria. Previous studies by X-ray crystallography have shown that full-length ArnA forms a three-bladed propeller-shaped hexamer. Here, the structures of ArnA determined by cryo-electron microscopy (cryo-EM) reveal that ArnA exists in two 3D architectures, hexamer and tetramer. This is the first observation of a tetrameric ArnA. The hexameric cryo-EM structure is similar to previous crystal structures but shows differences in domain movements and conformational changes. We propose that ArnA oligomeric states are in a dynamic equilibrium, where the hexamer state is energetically more favorable, and its domain movements are important for cooperating with downstream enzymes in the lipid A-Ara4N modification pathway. The results provide us with new possibilities to explore inhibitors targeting ArnA.
History
Deposition
Jan 14, 2019
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Header (metadata) release
Jan 23, 2019
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Map release
Aug 7, 2019
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Update
Dec 2, 2020
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Current status
Dec 2, 2020
Processing site: RCSB / Status: Released
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