Incorporation of D-alanine into lipoteichoic acid and wall teichoic acid in Bacillus subtilis. Identification of genes and regulation.
The Bacillus subtilis dlt operon (D-alanyl-lipoteichoic acid) is responsible for D-alanine esterification of both lipoteichoic acid (LTA) and wall teichoic acid (WTA). The dlt operon contains five genes, dltA-dltE. Insertional inactivation of dltA-dltD results in complete absence of D-alanine from both LTA and WTA. Based on protein sequence similarity with the Lactobacillus casei dlt gene products (Heaton, M. P., and Neuhaus, F. C. (1992) J. Bacteriol. 174, 4707-4717), we propose that dltA encodes the D-alanine-D-alanyl carrier protein ligase (Dcl) and dltC the D-alanyl carrier protein (Dcp). We further hypothesize that the products of dltB and dltD are concerned with the transport of activated D-alanine through the membrane and the final incorporation of D-alanine into LTA. The hydropathy profiles of the dltB and dltD gene products suggest a transmembrane location for the former and an amino-terminal signal peptide for the latter. The incorporation of D-alanine into LTA and WTA did not separate in any of the mutants studied which indicates that either one and the same enzyme is responsible for D-alanine incorporation into both polymers or a separate enzyme, encoded outside the dlt operon, transfers the D-alanyl residues from LTA to WTA (Haas, R., Koch, H.-U., and Fischer, W. (1984) FEMS Microbiol. Lett. 21, 27-31). Inactivation of dltE has no effect on D-alanine ester content of both LTA and WTA, and at present we cannot propose any function for its gene product. Transcription analysis shows that the dlt operon is transcribed from a sigma D-dependent promoter and follows the pattern of transcription of genes belonging to the sigma D regulon. However, the turn off of transcription observed before sporulation starts seems to be dependent on the Spo0A and AbrB sporulation proteins and results in a D-alanine-free purely anionic LTA in the spore membrane. The dlt operon is dispensable for cell growth; its inactivation does not affect cell growth or morphology as described for L. casei.
Perego
M
M
Dipartimento Farmaceutico, Facolta' di Farmacia, Universita' degli Studi di Parma, Italy.
Glaser
P
P
Minutello
A
A
Strauch
M A
MA
Leopold
K
K
Fischer
W
W
D000409:Alanine / Q000378:metabolism*; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008070:Lipopolysaccharides / Q000378:metabolism*; D008969:Molecular Sequence Data; D009876:Operon; D013682:Teichoic Acids / Q000378:metabolism*
D008070:Lipopolysaccharides; D013682:Teichoic Acids; C009900:lipoteichoic acid; D000409:Alanine