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| Title | Cryo-electron microscopy structures of ArnA, a key enzyme for polymyxin resistance, revealed unexpected oligomerizations and domain movements. |
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| Journal, issue, pages | J Struct Biol, Vol. 208, Issue 1, Page 43-50, Year 2019 |
| Publish date | Oct 1, 2019 |
 Authors | Meng Yang / Yu Seby Chen / Muneyoshi Ichikawa / Daniel Calles-Garcia / Kaustuv Basu / Rayan Fakih / Khanh Huy Bui / Kalle Gehring /  |
| PubMed 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. |
 External links | J Struct Biol / PubMed:31344437 |
| Methods | EM (single particle) |
| Resolution | 6.6 - 7.8 Å |
| Structure data | EMDB-0456: The cryo-EM structure of hexameric ArnA EMDB-20352, PDB-6pik: |
| Source |
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 Keywords | ANTIBIOTIC / Polymyxin resistance / hexamer / tetramer |
escherichia coli dh5[alpha] (bacteria)