ジャーナル: Biomolecules / 年: 2025 タイトル: Structural Basis for Targeting the Bifunctional Enzyme ArnA. 著者: Xinyu Liu / Ruochen Yang / Libang Ren / Tong Li / Yanrong Li / Zhihua Yan / Yanrong Gao / Mingqi Yang / Jiazhi Li / 要旨: Polymyxin antibiotics are often the last line of defense against multidrug-resistant Gram-negative pathogens. A key resistance mechanism involves the addition of 4-amino-4-deoxy-L-arabinose (L-Ara4N) ...Polymyxin antibiotics are often the last line of defense against multidrug-resistant Gram-negative pathogens. A key resistance mechanism involves the addition of 4-amino-4-deoxy-L-arabinose (L-Ara4N) to lipid A, mediated by the bifunctional enzyme ArnA. However, the evolutionary rationale and structural basis for ArnA's domain fusion, hexameric assembly, and catalytic coordination remain mechanistically unresolved. Here, we integrate evolutionary genomics, high-resolution cryo-electron microscopy (cryo-EM), and computational protein design to provide a comprehensive mechanistic analysis of ArnA. Our evolutionary analysis reveals that the dehydrogenase (DH) and formyltransferase (TF) domains evolved independently and were selectively fused in Gammaproteobacteria, suggesting an adaptive advantage. A 2.89 Å cryo-EM structure of apo-ArnA resolves the flexible interdomain linker and reveals a DH-driven hexameric architecture essential for enzymatic activity. 3D variability analysis captures intrinsic conformational dynamics, indicating a molecular switch that may coordinate sequential catalysis and substrate channeling. Structure-based peptide inhibitors targeting the hexamerization and predicted ArnA-ArnB interaction interfaces were computationally designed, offering a novel strategy for disrupting L-Ara4N biosynthesis. These findings illuminate a previously uncharacterized structural mechanism of antimicrobial resistance and lay the groundwork for therapeutic intervention.
全体 : Bifunctional polymyxin resistance protein ArnA
全体
名称: Bifunctional polymyxin resistance protein ArnA
要素
細胞: Bifunctional polymyxin resistance protein ArnA
タンパク質・ペプチド: Bifunctional polymyxin resistance protein ArnA
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超分子 #1: Bifunctional polymyxin resistance protein ArnA
超分子
名称: Bifunctional polymyxin resistance protein ArnA / タイプ: cell / ID: 1 / 親要素: 0 / 含まれる分子: all
由来(天然)
生物種: Escherichia coli BW25113 (大腸菌)
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分子 #1: Bifunctional polymyxin resistance protein ArnA
分子
名称: Bifunctional polymyxin resistance protein ArnA / タイプ: protein_or_peptide / ID: 1 詳細: Sequence reference for Escherichia coli BW25113 is not available at the time of biocuration. Current sequence reference is from UniProt ID P77398. コピー数: 6 / 光学異性体: LEVO / EC番号: UDP-4-amino-4-deoxy-L-arabinose formyltransferase