The endogenous Bacillus subtilis (natto) plasmids pTA1015 and pTA1040 contain signal peptidase-encoding genes: identification of a new structural module on cryptic plasmids

Authors

  • Wilfried J.J. Meijer,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • Anne De Jong,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • G. Bea,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • A. Wisman,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • Harold Tjalsma,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • Gerard Venema,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • Sierd Bron,

    1. Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN, Haren (Gn), The Netherlands
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  • Jan Maarten Van Dijl

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    • *

      Present address (and for correspondence): Department of Biochemistry, Biocentre of the University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland. E-mail DIJL@UBACLU. UNIBAS.CH. Tel. (61) 2672172 Fax. (61) 2672148.


Abstract

Various strains of Bacillus subtilis (natto) contain small cryptic plasmids that replicate via the rolling-circle mechanism. Like plasmids from other Gram-positive bacteria, these plasmids are composed of several distinct structural modules. A new structural module was identified on the B. subtilis plasmids pTA1015 and pTA1040. It is composed of two genes: one specifies an unidentified protein with a putative signal peptide; and the other (sipP) specifies a functional type I signal peptidase (SPase). The homologous, but non-identical, sipP genes of the two plasmids are the first identified plasmid-specific SPase-encoding genes. With respect to structure and activity, the corresponding enzymes (denoted SipP) are highly similar to the chromosomally encoded SPase, SipS, of B. subtilis and several newly identified SPases of other bacilli. Our findings suggest that plasmid-encoded SPases have evolved because, under certain conditions, SPase can be a limiting factor for protein secretion in B. subtilis.

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