1YRW

Crystal Structure of E.coli ArnA Transformylase Domain

Summary for 1YRW

• Entry DOI: 10.2210/pdb1yrw/pdb
• Descriptor: protein ArnA (2 entities in total)
• Functional Keywords: rossmann fold; ob-like fold, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 32871.58

Authors

Gatzeva-Topalova, P.Z.,May, A.P.,Sousa, M.C. (deposition date: 2005-02-04, release date: 2005-04-12, Last modification date: 2023-08-23)

Primary citation

Gatzeva-Topalova, P.Z.,May, A.P.,Sousa, M.C.
Crystal structure and mechanism of the Escherichia coli ArnA (PmrI) transformylase domain. An enzyme for lipid A modification with 4-amino-4-deoxy-L-arabinose and polymyxin resistance.
Biochemistry, 44:5328-5338, 2005

PubMed Abstract: Gram-negative bacteria have evolved mechanisms to resist the bactericidal action of cationic antimicrobial peptides of the innate immune system and antibiotics such as polymyxin. The strategy involves the addition of the positively charged sugar 4-amino-4-deoxy-l-arabinose (Ara4N) to lipid A in their outer membrane. ArnA is a key enzyme in the Ara4N-lipid A modification pathway. It is a bifunctional enzyme catalyzing (1) the oxidative decarboxylation of UDP-glucuronic acid (UDP-GlcA) to the UDP-4' '-ketopentose [UDP-beta-(l-threo-pentapyranosyl-4' '-ulose] and (2) the N-10-formyltetrahydrofolate-dependent formylation of UDP-Ara4N. Here we demonstrate that the transformylase activity of the Escherichia coli ArnA is contained in its 300 N-terminal residues. We designate it the ArnA transformylase domain and describe its crystal structure solved to 1.7 A resolution. The enzyme adopts a bilobal structure with an N-terminal Rossmann fold domain containing the N-10-formyltetrahydrofolate binding site and a C-terminal subdomain resembling an OB fold. Sequence and structure conservation around the active site of ArnA transformylase and other N-10-formyltetrahydrofolate-utilizing enzymes suggests that the HxSLLPxxxG motif can be used to identify enzymes that belong to this family. Binding of an N-10-formyltetrahydrofolate analogue was modeled into the structure of ArnA based on its similarity with glycinamide ribonucleotide formyltransferase. We also propose a mechanism for the transformylation reaction catalyzed by ArnA involving residues N(102), H(104), and D(140). Supporting this hypothesis, point mutation of any of these residues abolishes activity.

PubMed: 15807526
DOI: 10.1021/bi047384g

Experimental method

X-RAY DIFFRACTION (1.7 Å)