2.3.1.191 D232A mutation causes a 10fold reduction in kcat and a striking increase in the KM for both substrates 696264 2.3.1.191 F41A mutation increases the KM for UDP-3-O-((3R)-3-hydroxymyristoyl)-a-D-glucosamine 30fold and kcat 5fold 696264 2.3.1.191 K194A mutation has little effect on activity 696264 2.3.1.191 K46A mutation causes 3fold increase in KM((3R)-3-hydroxymyristoyl-[acyl-carrier protein]) and has no effect on kcat 696264 2.3.1.191 M290A wild-type EcLpxD prefers (R,S)-3-hydroxymyristoyl-ACP over (R,S)-3-hydroxypalmitoyl-ACP by a factor of 3, whereas the M290A mutant has the opposite selectivity. Both wild-type and M290A EcLpxD rescue the conditional lethality of Escherichia coli RL25, a temperature-sensitive strain harboring point mutations in lpxD. Complementation with wild-type EcLpxD restores normal lipid A containing only N-linked hydroxymyristate to RL25 at 42°C, as judged by mass spectrometry, whereas the M290A mutant generates multiple lipid A species containing one or two longer hydroxy fatty acids in place of the usual (3R)-3-hydroxymyristate at positions 2 and 20 696356 2.3.1.191 M292A wild-type EcLpxD prefers (R,S)-3-hydroxymyristoyl-ACP over (R,S)-3-hydroxypalmitoyl-ACP by a factor of 3, mutant enzyme M292A prefers (R,S)-3-hydroxymyristoyl-ACP over (R,S)-3-hydroxypalmitoyl-ACP by a factor of 2.5 696356 2.3.1.191 additional information construction of lpx insertional knockout mutations or RNAi knock-down mutants -, 720913 2.3.1.191 additional information construction of lpxD1-null and lpxD2-null mutant strains, that show altered antibiotic susceptibility patterns, membrane permeability, but no innate immune responses -, 720944 2.3.1.191 N233A mutation causes a 10fold reduction in kcat and a striking increase in the KM for both substrates 696264 2.3.1.191 N240A causes less than a 2fold reduction in specific activity, when assayed at substrate concentrations at 2fold above KM with the purified proteins 696264