ThedltOperon in the Biosynthesis ofd-Alanyl-Lipoteichoic Acid inLactobacillus casei

Abstract
The d-alanine incorporation system allows Lactobacillus casei to modulate the chemical properties of lipoteichoic acid (LTA) and hence control its proposed functions, i.e., regulation of autolysin action, metal ion binding, and the electromechanical properties of the cell wall. The system requires the d-alanine-d-alanyl carrier protein ligase (Dcl) and the d-alanyl carrier protein (Dcp). Our results indicate that the genes for these proteins are encoded in the dit operon and that this operon contains at least 2 other genes, dltB and dltD. The aim of this paper is to describe the genetic organization of the operon, the role of the d-alanyl carrier protein, and the function of the putative protein encoded by dltB in the intramembranal translocation of the activated d-alanine.