Duplication of teichoic acid biosynthetic genes in Staphylococcus aureus leads to functionally redundant poly(ribitol phosphate) polymerases.
Wall teichoic acids are anionic phosphate-rich polymers that are part of the complex meshwork of carbohydrates that make up the gram-positive cell wall. These polymers are essential to the proper rod-shaped morphology of Bacillus subtilis and have been shown to be an important virulence determinant in the nosocomial opportunistic pathogen Staphylococcus aureus. Together, sequence-based studies, in vitro experiments with biosynthetic proteins, and analyses of the chemical structure of wall teichoic acid have begun to shed considerable light on our understanding of the biogenesis of this polymer. Nevertheless, some paradoxes remain unresolved. One of these involves a putative duplication of genes linked to CDP-ribitol synthesis (tarI'J' and tarIJ) as well as poly(ribitol phosphate) polymerization (tarK and tarL) in S. aureus. In the work reported here, we performed careful studies of the dispensability of each gene and discovered a functional redundancy in the duplicated gene clusters. We were able to create mutants in either of the putative ribitol phosphate polymerases (encoded by tarK and tarL) without affecting teichoic acid levels in the S. aureus cell wall. Although genes linked to CDP-ribitol synthesis are also duplicated, a null mutant in only one of these (tarI'J') could be obtained, while tarIJ remained essential. Suppression analysis of the tarIJ null mutant indicated that the mechanism of dysfunction in tarI'J' is due to poor translation of the TarJ' enzyme, which catalyzes the rate-limiting step in CDP-ribitol formation. This work provides new insights into understanding the complex synthetic steps of the ribitol phosphate polymer in S. aureus and has implications on specifically targeting enzymes involved in polymer biosynthesis for antimicrobial design.
Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1200 Main Street West, Hamilton, Ontario L8N 3Z5, Canada.
Mark P
MP
Pereira
Michael A
MA
D'Elia
Justyna
J
Troczynska
Eric D
ED
Brown
D002473:Cell Wall / Q000737:chemistry; D017353:Gene Deletion; D023061:Gene Order; D020131:Genes, Duplicate; D020043:Genes, Essential; D005816:Genetic Complementation Test; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D015394:Molecular Structure; D016254:Mutagenesis, Insertional; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D013682:Teichoic Acids / Q000032:analysis; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics* / Q000378:metabolism*
D013682:Teichoic Acids; D017855:Transferases (Other Substituted Phosphate Groups); C022719:CDPribitol ribitolphosphotransferase