title: Monofunctional transglycosylases are not essential for Staphylococcus aureus cell wall synthesis.
abstract: The polymerization of peptidoglycan is the result of two types of enzymatic activities: transglycosylation, the formation of linear glycan chains, and transpeptidation, the formation of peptide cross-bridges between the glycan strands. Staphylococcus aureus has four penicillin binding proteins (PBP1 to PBP4) with transpeptidation activity, one of which, PBP2, is a bifunctional enzyme that is also capable of catalyzing transglycosylation reactions. Additionally, two monofunctional transglycosylases have been reported in S. aureus: MGT, which has been shown to have in vitro transglycosylase activity, and a second putative transglycosylase, SgtA, identified only by sequence analysis. We have now shown that purified SgtA has in vitro transglycosylase activity and that both MGT and SgtA are not essential in S. aureus. However, in the absence of PBP2 transglycosylase activity, MGT but not SgtA becomes essential for cell viability. This indicates that S. aureus cells require one transglycosylase for survival, either PBP2 or MGT, both of which can act as the sole synthetic transglycosylase for cell wall synthesis. We have also shown that both MGT and SgtA interact with PBP2 and other enzymes involved in cell wall synthesis in a bacterial two-hybrid assay, suggesting that these enzymes may work in collaboration as part of a larger, as-yet-uncharacterized cell wall-synthetic complex.
authors: Laboratory of Bacterial Cell Biology, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República, Apartado 2781-901 Oeiras, Portugal.
authors: Patricia
authors: P
authors: Reed
authors: Helena
authors: H
authors: Veiga
authors: Ana M
authors: AM
authors: Jorge
authors: Mohammed
authors: M
authors: Terrak
authors: Mariana G
authors: MG
authors: Pinho
mesh_terms: D001426:Bacterial Proteins; D002473:Cell Wall / Q000378:metabolism*; D017353:Gene Deletion; D020043:Genes, Essential; D006602:Hexosyltransferases; D050296:Microbial Viability; D046915:Penicillin-Binding Proteins / Q000235:genetics / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism*; D046928:Peptidoglycan Glycosyltransferase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D006602:Hexosyltransferases; C433790:MGT protein, Staphylococcus aureus; D046928:Peptidoglycan Glycosyltransferase