3t57

Publication Abstract from PubMed

The UDP-N-acetylglucosamine (UDP-GlcNAc) acyltransferase, encoded by lpxA, catalyzes the first step of lipid A biosynthesis in Gram-negative bacteria, the (R)-3-hydroxyacyl-ACP-dependent acylation of the 3-OH group of UDP-GlcNAc. Recently, we demonstrated that the Arabidopsis thaliana orthologs of six enzymes of the bacterial lipid A pathway produce lipid A precursors with structures similar to those of Escherichia coli lipid A precursors [Li, C., et al. (2011) Proc. Natl. Acad. Sci. U.S.A. 108, 11387-11392]. To build upon this finding, we have cloned, purified, and determined the crystal structure of the A. thaliana LpxA ortholog (AtLpxA) to 2.1 A resolution. The overall structure of AtLpxA is very similar to that of E. coli LpxA (EcLpxA) with an alpha-helical-rich C-terminus and characteristic N-terminal left-handed parallel beta-helix (LbetaH). All key catalytic and chain length-determining residues of EcLpxA are conserved in AtLpxA; however, AtLpxA has an additional coil and loop added to the LbetaH not seen in EcLpxA. Consistent with the similarities between the two structures, purified AtLpxA catalyzes the same reaction as EcLpxA. In addition, A. thaliana lpxA complements an E. coli mutant lacking the chromosomal lpxA and promotes the synthesis of lipid A in vivo similar to the lipid A produced in the presence of E. coli lpxA. This work shows that AtLpxA is a functional UDP-GlcNAc acyltransferase that is able to catalyze the same reaction as EcLpxA and supports the hypothesis that lipid A molecules are biosynthesized in Arabidopsis and other plants.

Activity and Crystal Structure of Arabidopsis thalianaUDP-N-Acetylglucosamine Acyltransferase.,Joo SH, Chung HS, Raetz CR, Garrett TA Biochemistry. 2012 May 14. PMID:22545860^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.