Role of the unique, non-essential phosphatidylglycerol::prolipoprotein diacylglyceryl transferase (Lgt) in .

Bacterial lipoproteins are secreted proteins that are post-translationally lipidated. Following synthesis, preprolipoproteins are transported through the cytoplasmic membrane via the Sec or Tat translocon. As they exit the transport machinery, they are recognized by a phosphatidylglycerol::prolipoprotein diacylglyceryl transferase (Lgt), which converts them to prolipoproteins by adding a diacylglyceryl group to the sulfhydryl side chain of the invariant Cys residue. Lipoprotein signal peptidase (LspA or signal peptidase II) subsequently cleaves the signal peptide, liberating the α-amino group of Cys, which can eventually be further modified. Here, we identified the and genes from and found that they are unique but not essential. We found that Lgt is necessary for the acylation and membrane anchoring of two model lipoproteins expressed in this species: MusE, a maltose-binding lipoprotein, and LppX, a lipoprotein. However, Lgt is not required for these proteins' signal peptide cleavage, or for LppX glycosylation. Taken together, these data show that in the association of some lipoproteins with membranes through the covalent attachment of a lipid moiety is not essential for further post-translational modification.