1z74
From Proteopedia
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Crystal Structure of E.coli ArnA dehydrogenase (decarboxylase) domain, R619Y mutant
Overview
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.
About this Structure
1Z74 is a Single protein structure of sequence from Escherichia coli with SO4 as ligand. Full crystallographic information is available from OCA.
Reference
Structure and mechanism of ArnA: conformational change implies ordered dehydrogenase mechanism in key enzyme for polymyxin resistance., Gatzeva-Topalova PZ, May AP, Sousa MC, Structure. 2005 Jun;13(6):929-42. PMID:15939024
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