Part:BBa_K5150013

PhoD signal peptide

The twin-arginine translocase (Tat) system is a specialized export pathway in certain bacteria that transports fully folded proteins, including their cofactors, across cellular membranes. This system can efficiently move tightly folded proteins and multimeric enzyme complexes from the cytosol of Bacillus subtilis into the surrounding medium. Notably, B. subtilis has two distinct Tat systems designed for specific cargo: the phosphodiesterase PhoD and the iron-dependent peroxidase YwbN [1]. The Tat translocase for PhoD is particularly well-studied due to its selective targeting in foreign organisms and simple composition. In B. subtilis, the PhoD translocation machinery comprises two integral membrane proteins, TatAd and TatCd. The TatCd receptor identifies PhoD through its N-terminal signal peptide, which features a conserved twin-arginine motif, facilitating the assembly of a translocation-competent pore along with the pore-forming unit TatAd ^[1].

**Figure 1. Diagram showing how the signal peptide PhoD is useful for the secretion of recombinant proteins**

Proteins destined for membrane transport are expressed as preproteins with specific N-terminal tags that guide them to the appropriate translocation machinery. Precursors with a twin-arginine (RR/KR) signal peptide can fold in the cytoplasm with the assistance of cofactors before translocation. These proteins are then transported through a channel formed by the Tat protein complex (Tat translocase). After translocation and processing by type I signal peptidase, the folded mature proteins are secreted into the growth medium. The signal peptide can be fused to the N-terminus of a recombinant protein, and it will be cleaved during the translocation across the cell membrane by signal peptidases ^[2].

Sequence and Features

Assembly Compatibility:

10
COMPATIBLE WITH RFC[10]
12
COMPATIBLE WITH RFC[12]
21
COMPATIBLE WITH RFC[21]
23
COMPATIBLE WITH RFC[23]
25
COMPATIBLE WITH RFC[25]
1000
COMPATIBLE WITH RFC[1000]

References

↑ Müller, S. D., De Angelis, A. A., Walther, T. H., Grage, S. L., Lange, C., Opella, S. J., & Ulrich, A. S. (2007). Structural characterization of the pore forming protein TatAd of the twin-arginine translocase in membranes by solid-state 15N-NMR. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1768(12), 3071-3079.
↑ Senger, J., Seitl, I., Pross, E., & Fischer, L. (2024). Secretion of the cytoplasmic and high molecular weight β-galactosidase of Paenibacillus wynnii with Bacillus subtilis. Microbial Cell Factories, 23(1), 170.

[1] Müller, S. D., De Angelis, A. A., Walther, T. H., Grage, S. L., Lange, C., Opella, S. J., & Ulrich, A. S. (2007). Structural characterization of the pore forming protein TatAd of the twin-arginine translocase in membranes by solid-state 15N-NMR. Biochimica et Biophysica Acta (BBA)-Biomembranes, 1768(12), 3071-3079.

[2] Senger, J., Seitl, I., Pross, E., & Fischer, L. (2024). Secretion of the cytoplasmic and high molecular weight β-galactosidase of Paenibacillus wynnii with Bacillus subtilis. Microbial Cell Factories, 23(1), 170.

[1]

[2]