Lyme disease is the most common tick-born disease in the United States, with almost half a million cases diagnosed every year. Lyme disease is caused by the bacterium Borrelia burgdorferi (Bb), which is transmitted to humans when they are bitten by an infected tick. Bb does not produce any toxins, and the pathogenesis of Lyme disease in humans appears to be due to a strong immune response to the bacterium itself. The resulting long-lasting inflammatory response can damage several different organs including the brain, peripheral and central nervous systems, heart, and joints.
When Bb infection is recognized immediately, usually by a characteristic bullseye shaped rash around the site of the tick bite, Lyme disease can usually be cured by treatment with antibiotics. However, 20% to 30% of people with Lyme disease will not have the rash, and many will not know they are infected in time to be cured. This has led to a great interest in developing a vaccine to prevent Lyme disease.
Many people with Lyme disease have antibodies to a cholesterol-based glycolipid, ACGal (produced by Bb), leading some scientists to propose ACGal as a potential Lyme disease vaccine candidate. How the bacterium produces ACGal, and the related CGal, has been unclear since Bb cannot make its own cholesterol and must modify cholesterol from the host.
In recent work, Hove et al identified a potential galactosyltransferase, BB0572, in the Bb genome by searching the Bb genome for sequences similar to a known glycosyltransferase from a related bacterium. The group demonstrated that the gene encoding BB0572 was actively expressed by the Bb bacterium. To prove BB0572 has galactosyltransferase activity, the group carried out assays with 14C-labeled cholesterol and extracts of Bb bacteria and of E coli engineered to overexpress the gene for the BB0572 protein. The products of the assay were separated using thin-layer chromatography (TLC), and the radioactive products detected on the TLC plates using a Sapphire Biomolecular Imager. The results indicate CGal can be synthesized by BB0572. ACGal was not detected, possibly because the acyl donor was missing from the reaction.
The identification of BB0572 as the enzyme likely responsible for the synthesis of CGal and ACGal opens up new areas of research including identifying how ACGal is synthesized from CGal and studying the importance of these lipids to both Bb physiology and the development of Lyme disease.
In addition to phosphor imaging to detect radiolabeled targets, the Sapphire Biomolecular Imager provides chemiluminescence, multi-channel fluorescence, NIR fluorescence, densitometry, and white light imaging of blots, gels, tissues, and more.
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