2018 Volume 21 Pages 51-55
Lipid A is known to exhibit various immunostimulating activities, and acyloxyacyl structure formed by 3-hydroxy and non-polar fatty acids is important for the activity. Although the relationship between the activity and the acyloxyacyl structure has been precisely investigated using chemically synthesized lipid A, modifications of lipid A by genetic methods have not been much attempted. In the present study, the double-knockout mutant of Escherichia coli with disrupted lauroyl-and palmitoyltransferase genes (KGu0377) was constructed, and transformed with palmitoyltransferase gene from Salmonella (pagP) or from Campylobacter jejuni to obtain strains KGu0431 and KGu0441, respectively. The mutant produced the lipid A without acyloxyacyl structure, showed slower growth at 37°C, and was very sensitive to polymyxin B. The transformant KGu0431 could grow as rapid as the wild-type strain and showed the partially restored resistance to polymyxin B. Another transformant KGu0441 also showed the similar recovery of polymyxin B resistance, but its growth was still slower than the wild-type strain. Mass spectrometric analysis revealed that KGu0431 produced considerable amount of penta-acylated lipid A with palmitic acid. On the other hand, KGu0441 produced a small amount of hexa-acylated lipid A with palmitic and myristic acids. The IL-6 inducing activity of KGu0377 LPS was much weaker than that of the wild-type strain, as expected, and the activity of LPS from the transformants was at the same level as that of KGu0377 or only slightly restored. The present study showed the possibility to produce lipid A with novel structures using various acyltransferases from other bacteria.
