Part:BBa_K1351043

Canibalism toxin SDP of B. subtilis

Background

The sdp-System of B. subtilis consists of two operons: The sdpABC operon, coding for the production and secretion of the cannibalism toxin SDP and the sdpRI operon responsible for the regulation and production of the immunity protein SdpI (Fig. 1).

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Fig. 1. Gene organization for the sdpABC sdpRI operons. The hairpin symbolizes thetranscriptional terminators. [1]

In vegetative cells, both operons are repressed by the unstable AbrB regulator. However, during early stages of sporulation AbrB itself is repressed by the master regulator of sporulation Spo0A, making ''sdpABC'' and ''sdpRI'' accessible for RNA polymerase. [1] === The ''sdpABC'' Operon – Production and Secretion of the Cannibalism Toxin SDP === The production of the Cannibalism Toxin SDP is a multi-step process. The ''sdpC'' sequence encodes the Pro-SdpC1-203,,which is translated by the ribosome.It is a precursor peptide which needs to be processed by a signal peptidases and the two membrane proteins SdpA and SdpB to become functional. This active form of SDP is a 42-amino-acid antimicrobial peptide (AMP) containing a disulfide bond between two cysteine residues located at the N-terminus.(Fig. 2). [2]] [[File:Background Fig.2.png|thumb|800px|center|Fig. 2. SDP production requires multiple steps. In the cytosol, the full length SdpC (pro-SdpC1-203) is secreted via the Sec pathway. Following secretion, the signal peptidases SipS and SipT cleave the N-terminal signal peptide sequence of SdpC. Disulfide bond formation occurs independently of SdpAB. Finally, posttranslational cleavage of SdpC occurs via SdpAB to produce a 42-amino-acid SDP that will be secreted extracellulary as the active SDP peptide. [2]]] SDP has been shown to be a very effective AMP against a variety of Gram-positive bacteria in the Phylum of the Firmicutes (Fig. 3). It rapidly collapses the proton motive force (PMF), thus inducing autolysis. [3] [[File:Background Fig.3.png|thumb|600px|center|Fig. 3. SDP inhibition curves for pathogenic microbes. Relative growth of the strains named abovewith the presence of increasing concentrations of SDP is shown in the curve. As a negative control the gram-negative bacteria ''K. pneumoniae'' and ''P. aeruginosa'' are depicted, which are unaffected by the toxin SDP, as it specifically targets gram-positive bacteria. ''B. subtilis'' is a gram-positive bacteria, but expresses the immunity protein SdpI and is therefore relatively resistent to the toxin SDP. the ''Stapylococcus'' species (also MRSA) though are quite drastically reduced in the presence of the SDP. [4]]] === Sources === [1] Gonzalez-Pastor, J. E. (2011). "Cannibalism: a social behavior in sporulating Bacillus subtilis." FEMS Microbiol Rev 35(3): 415-424. [2] Perez Morales, T. G., et al. (2013). "Production of the cannibalism toxin SDP is a multistep process that requires SdpA and SdpB." J Bacteriol 195(14): 3244-3251. [3] Lamsa, A., et al. (2012). "The Bacillus subtilis cannibalism toxin SDP collapses the proton motive force and induces autolysis." Mol Microbiol 84(3): 486-500. Sequence and Features BBa_K1351043 SequenceAndFeatures