title: The importance of the Tat-dependent protein secretion pathway in Streptomyces as revealed by phenotypic changes in tat deletion mutants and genome analysis.
abstract: Streptomyces are Gram-positive soil bacteria that are used industrially, not only as a source of medically important natural compounds, but also as a host for the secretory production of a number of heterologous proteins. A good understanding of the different secretion processes in this organism is therefore of major importance. The functionality of the recently discovered bacterial twin-arginine translocation (Tat) pathway has already been shown in Streptomyces lividans. Here, the aberrant phenotype of S. lividans DeltatatB and DeltatatC single mutants is described. Both mutants are characterized by a dispersed growth in liquid medium, an impaired morphological differentiation on solid medium and growth retardation. To reveal the extent to which the Tat pathway is used in Streptomyces, putative Tat-dependent precursor proteins of Streptomyces coelicolor, a very close relative of S. lividans, and of Streptomyces avermitilis, of which the genomes have been completely sequenced, were identified by a modified version of the TATFIND computer program designed by Rose and colleagues [Rose, R. W., Brüser, T., Kissinger, J. C. & Pohlschröder, M. (2002). Mol Microbiol 45, 943-950]. A list of 230 precursor proteins was obtained; this is the highest number of putative Tat substrates found in any genome so far. In addition to the Streptomyces antibioticus tyrosinase, it was also demonstrated that the secretion of the S. lividans xylanase C is Tat-dependent. The predicted Tat substrates belong to a variety of protein classes, with a high number of proteins functioning in degradation of macromolecules, in binding and transport, and in secondary metabolism. Only a minor fraction of the proteins seem to bind a cofactor. The aberrant phenotype of the DeltatatB and DeltatatC mutants together with the high number of putative Tat-dependent substrates suggests that the Streptomyces Tat pathway has a distinct and more important role in protein secretion than in most other bacteria.
authors.affiliation: Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
authors.forename: Kristien
authors.initials: K
authors.lastname: Schaerlaekens
authors.affiliation: Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
authors.forename: Lieve
authors.initials: L
authors.lastname: Van Mellaert
authors.affiliation: Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Lammertyn
authors.affiliation: Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
authors.forename: Nick
authors.initials: N
authors.lastname: Geukens
authors.affiliation: Laboratory of Bacteriology, Rega Institute, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium.
authors.forename: Jozef
authors.initials: J
authors.lastname: Anné
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D043364:Endo-1,4-beta Xylanases / Q000378:metabolism; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010641:Phenotype; D021382:Protein Sorting Signals / Q000235:genetics; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism*; D020860:Subtilisin / Q000037:antagonists & inhibitors
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; C408585:twin-arginine translocase complex, E coli; D014442:Monophenol Monooxygenase; D043364:Endo-1,4-beta Xylanases; D020860:Subtilisin