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 dlt 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.

A Continuum of Anionic Charge: Structures and Functions ofd-Alanyl-Teichoic Acids in Gram-Positive Bacteria

“…Isolation of the gene encoding the activating enzyme (dltA) (Fig. 9) from L. rhamnosus ATCC 7469 provided the key for identifying the role of this enzyme in D-alanine incorporation (209,367). The enzyme is a member of a large protein on May 10, 2018 by guest http://mmbr.asm.org/ family that both activates and transfers amino or fatty acids via a 4Ј-phosphopantetheine prosthetic group of a carrier protein or coenzyme A CoA (262).…”

“…However, the functions of TAs within the wall matrix have been more difficult to define. The D-alanyl esters of these polymers, resulting from a single D-alanine incorporation system encoded by the dlt (for "D-alanyl-LTA") operon (209,367,383), constitute important substituents for modulating the properties of the envelope in many species. For this reason, knowledge of these ester residues is essential for understanding the functions of TAs in bacterial physiology as well as in host-mediated responses.…”

Regulation of bacterial virulence gene expression by cell envelope stress responses

“…131,132 The products of the dltABCD operon incorporate D-alanine into LTAs, which can then be transferred to WTAs by transacetylation. 154,155 Therefore, inactivation of the dlt operon increases the net negative charge of the cell envelope. Consistent with this, dlt null mutants of Gram-positive pathogens have increased sensitivity to CAMPs, increased killing by human neutrophils and reduced virulence in animal models of infection.…”

cwrA, a gene that specifically responds to cell wall damage in Staphylococcus aureus

“…The dlt operon is responsible for the D-alanylation of wall teichoic acids (WTAs) and lipoteichoic acids (LTAs), components of the cell envelope in S. aureus (Neuhaus et al, 1996). Teichoic acids represent the most abundant polyanions of the Gram-positive cell envelope (Fischer, 1994), and altering their charge properties through esterification with D-alanine has pleiotropic effects which can change autolytic enzyme activity (Wecke et al, 1996), cation binding (Hughes et al, 1973), susceptibility to cationic peptides (Peschel et al, 1999), virulence (Collins et al, 2002) and biofilm formation (Gross et al, 2001).…”