PMID:15939024
| Citation |
Gatzeva-Topalova, PZ, May, AP and Sousa, MC (2005) Structure and mechanism of ArnA: conformational change implies ordered dehydrogenase mechanism in key enzyme for polymyxin resistance. Structure 13:929-42 |
|---|---|
| Abstract |
The modification of lipid A with 4-amino-4-deoxy-L-arabinose (Ara4N) allows gram-negative bacteria to resist the antimicrobial activity of cationic antimicrobial peptides and antibiotics such as polymyxin. ArnA is the first enzyme specific to the lipid A-Ara4N pathway. It contains two functionally and physically separable domains: a dehydrogenase domain (ArnA_DH) catalyzing the NAD+-dependent oxidative decarboxylation of UDP-Glucuronic acid (UDP-GlcA), and a transformylase domain that formylates UDP-Ara4N. Here, we describe the crystal structure of the full-length bifunctional ArnA with UDP-GlcA and ATP bound to the dehydrogenase domain. Binding of UDP-GlcA triggers a 17 A conformational change in ArnA_DH that opens the NAD+ binding site while trapping UDP-GlcA. We propose an ordered mechanism of substrate binding and product release. Mutation of residues R619 and S433 demonstrates their importance in catalysis and suggests that R619 functions as a general acid in catalysis. The proposed mechanism for ArnA_DH has important implications for the design of selective inhibitors. |
| Links |
PubMed PMC2997725 Online version:10.1016/j.str.2005.03.018 |
| Keywords |
Adenosine Triphosphate/metabolism; Amino Sugars/chemistry; Amino Sugars/metabolism; Anti-Bacterial Agents/pharmacology; Binding Sites; Catalysis; Crystallography, X-Ray; Dimerization; Drug Resistance, Microbial; Hydrogen Bonding; Hydroxymethyl and Formyl Transferases/chemistry; Hydroxymethyl and Formyl Transferases/metabolism; Ligands; Models, Molecular; Molecular Conformation; Mutation; Oxidation-Reduction; Polymyxins/pharmacology; Protein Binding; Protein Structure, Secondary; Protein Structure, Tertiary; Spectrum Analysis, Raman; Substrate Specificity; Uridine Diphosphate Glucose Dehydrogenase/chemistry; Uridine Diphosphate Glucose Dehydrogenase/genetics; Uridine Diphosphate Glucuronic Acid/chemistry; Uridine Diphosphate Glucuronic Acid/metabolism |
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