Investigation of a choline phosphate synthesis pathway in Streptococcus pneumoniae: evidence for choline phosphate cytidylyltransferase activity

Abstract The antimicrobial peptide epidermin is distinguished by thioether amino acids such as mso -lanthionine, 3-methyllanthionine, and 2-aminovinylcysteine. The enzyme EpiB, encoded on a plasmid of the producing strain Staphylococcus epidermidis Tü3298, is very likely involved in the formation of these unusual amino acids. In order to obtain high-level production of EpiB, an improved staphylococcal expression vector based on the xylose-inducible xylA promoter of Staphylococcus xylosus was constructed. As shown by the expression of a lipase reporter gene, the new plasmid pTX15 mediated a considerably higher expression level after induction and a lower background expression level in the uninduced state than the previously described vector pCX15. The epiB gene was inserted in pTX15 and expressed in Staphylococcus carnosus . The EpiB protein was detected both in the cytoplasmic and the membrane fraction and was partially purified in three steps.