Fatty acids of lipoproteins CagT and Lpp20.

Bacterial lipoproteins are post-translationally modified by the addition of acyl chains that anchor the protein to bacterial membranes. This modification includes two ester-linked and one amide-linked acyl chain on lipoproteins from Gram-negative bacteria. lipoproteins have important functions in pathogenesis (including delivering the CagA oncoprotein to mammalian cells) and are recognized by host innate and adaptive immune systems. The number and variety of acyl chains on lipoproteins impact the innate immune response through Toll-like receptor 2. The acyl chains added to lipoproteins are derived from membrane phospholipids. membrane phospholipids have previously been shown to consist primarily of C14:0 and C19:0 cyclopropane-containing acyl chains. However, the acyl composition of lipoproteins has not been determined. In this study, we characterized the acyl composition of two representative lipoproteins, Lpp20 and CagT. Fatty acid methyl esters were prepared from both purified lipoproteins and analyzed by gas chromatography-mass spectrometry. For comparison, we also analyzed phospholipids. Consistent with previous studies, we observed that the phospholipids contain primarily C14:0 and C19:0 cyclopropane-containing fatty acids. In contrast, both the ester-linked and amide-linked fatty acids found in lipoproteins were observed to be almost exclusively C16:0 and C18:0. A discrepancy between the acyl composition of membrane phospholipids and lipoproteins as reported here for has been previously reported in other bacteria including and . We discuss possible mechanisms.IMPORTANCEColonization of the stomach by is an important risk factor in the development of gastric cancer, the third leading cause of cancer-related death worldwide. persists in the stomach despite an immune response against the bacteria. Recognition of lipoproteins by TLR2 contributes to the innate immune response to . However, the role of lipoproteins in bacterial persistence is poorly understood. As the host response to lipoproteins depends on the acyl chain content, defining the acyl composition of lipoproteins is an important step in characterizing how lipoproteins contribute to persistence.