title: The NucE and NucD lysis proteins are not essential for secretion of the Serratia marcescens extracellular nuclease.
abstract: The nuclease of Serratia marcescens is an extracellular protein encoded by the nucA gene. Pre-nuclease carries a typical 21-amino-acid N-terminal signal sequence that interacts with the Sec machinery to allow the translocation of nuclease to the periplasm. In Escherichia coli the nuclease remains in the periplasm; however, S. marcescens has the capacity to secrete nuclease extracellularly. The nucC operon carrying the nucEDC genes of S. marcescens has been identified previously. NucC is a transcriptional activator necessary for expression of nuclease as well as the extracellular bacteriocin 28b. NucE resembles and can act as a bacteriophage holin, whereas NucD has homology to bacteriophage lysozyme-like proteins. When present on a multicopy plasmid, the nucC operon, and specifically the nucED genes, appeared to allow extracellular secretion of nuclease from E. coli. Here experiments are reported which demonstrate that, when the nucC operon was placed in the E. coli chromosome in single copy, nuclease secretion was lost and nuclease remained periplasmic. The converse experiment, deletion of the nucE and nucD genes from the chromosome of S. marcescens, likewise had no effect on nuclease secretion by S. marcescens. It is concluded therefore that NucD and NucE are not necessary for nuclease secretion.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Strych
authors.forename: Wenping
authors.initials: W
authors.lastname: Dai
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Benedik
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D017353:Gene Deletion; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D011994:Recombinant Proteins / Q000378:metabolism; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; C108623:NucE protein, Serratia marcescens; D011994:Recombinant Proteins; D004706:Endodeoxyribonucleases; D004722:Endoribonucleases; C021835:Serratia marcescens nuclease