Signal-sequence-independent secretion of the staphylococcal nuclease in Mycobacterium smegmatis.
Staphylococcus aureus nuclease is a small, secreted protein which has been successfully used as a reporter system to identify exported products in Lactococcus lactis. Here, biochemical evidence is provided that the nuclease is exported by Mycobacterium smegmatis in the presence, but also in the absence of a signal sequence, and thus probably independently of the Sec translocation pathway. This implies that the nuclease should not be used as a reporter system in mycobacteria for the identification of exported products, despite what has been reported previously in the literature. The nuclease can be extended to create hybrid proteins that remain compatible with its secretion, whereas some other shorter fusions are not tolerated. This suggests that correct folding is required for efficient export. Extensive mutational analysis did not identify a specific secretion pathway. This suggests that the nuclease may be exported by different redundant systems or that components of this alternative Sec pathway are essential for bacterial survival.
Recchi
Chiara
C
Unité de Génétique Mycobactérienne, Institut Pasteur, 25, Rue du Dr Roux, 75724 Paris cedex 15, France1.
Rauzier
Jean
J
Unité de Génétique Mycobactérienne, Institut Pasteur, 25, Rue du Dr Roux, 75724 Paris cedex 15, France1.
Gicquel
Brigitte
B
Unité de Génétique Mycobactérienne, Institut Pasteur, 25, Rue du Dr Roux, 75724 Paris cedex 15, France1.
Reyrat
Jean-Marc
JM
Unité de Génétique Mycobactérienne, Institut Pasteur, 25, Rue du Dr Roux, 75724 Paris cedex 15, France1.
D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D017930:Genes, Reporter; D008836:Micrococcal Nuclease / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020102:Mycobacterium smegmatis / Q000235:genetics* / Q000502:physiology; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D004269:DNA, Bacterial; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D008836:Micrococcal Nuclease