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Subtilosin-A is a bacteriocin, antimicrobial peptide that was first discovered in Bacillus subtilis 168. Subtilosin-A is classified as a class V bacteriocin because it has unique circular structure compared to another bacteriocin. The circular structure of this protein is caused by disulfide bond that formed in post-translation modification
Subtilosin A was coded by SboA gene that exist in the genome of many strains of B.subtilis. Modification proteins that help post-translational modification of Subtilosin A are located downstream. Genes that encode modification proteins of Subtilosin A was AlbA, AlbB, AlbC, AlbD, AlbE, AlbF, and AlbG. Aside from post-modifying the Subtilosin-A, some of the genes also transport the Subtilosin-A to extracellular compartment. SboA gene and AlbA-AlbG genes make a complex cluster of gene called operon. SboA operon is about 6816 base pairs, meanwhile SboA gene itself only 132 basepairs with its protein weight about 40 kDa (43 amino acid).
There are three possibilities of the mechanism of action of Subtilosin A.
The first possibility that cause cell death is interaction of Subtilosin A within receptor in cell membrane and its trigger cell lysis.
Second possibility is interaction of Subtilosin A to membrane plasma that cause disorientation of phospholipids which will make pore in cell membrane.
Third possibility is Subtilosin A cause malfunction of some chemical pathway that will disturb physiology of cell. Recent observation shows that Subtilosin A tied directly to membrane plasma.
Subtilosin A tied with membrane plasma at high concentration because this protein has its function when it was multimeric, it has to tied up with another Subtilosin A before it could tied with membrane plasma and disorientate its phospholipids. Subtilosin A become monomeric when concentraiion of this protein is below 16.4 uM. Beside of Subtilosin A concentration, type of membrane plasma also factor that affecting Subtilosin A activity. Membrane plasma that contain many of cholesterol just like mammalian cell membrane plasma, will not break because cholesterol intercalate between acyl chain in phospholipids. Because of this information, we can predict that Subtilosin A can disorientate phospholipids in cell that has no cholesterol or only a few of it. the other cell that has been known could be break down easily by Subtilosin A is sperm cell.
Recent studies shows that Subtilosin A can decrease mobility of sperm cell. Subtilosin A break down membrane plasma and coil tail of sperm cell. This protein also known that it doesn’t affect population of vaginal normal flora such as Lactobacillus. Not only this protein doesn’t affect population of vaginal normal flora, it also has antimicrobial activity to microbes that cause bacterial vaginoses (BV) such as L. monocytogenes, G. vaginalis, & S. agalactiae.
Because the antispermicidal activity of this bacteriocin, not affecting the vaginal normal flora and decreasing number of harmful microbes in vagina, Subtilosin A is the best candidate for contraception
To control when the Subtilosin-A was expressed, we designed a toggle switch based on the activation-repression of promoters. We used pXyl, lacI, pHyperSpank, XylR
Reference
Sutyak K, Anderson R, Dover S, Feathergill K, Aroutcheva A, Faro S et al. Spermicidal Activity of the Safe Natural Antimicrobial Peptide Subtilosin. Infectious Diseases in Obstetrics and Gynecology. 2008;2008:1-6
Zheng G, Hehn R, Zuber P. Mutational Analysis of the sbo-alb Locus of Bacillus subtilis: Identification of Genes Required for Subtilosin Production and Immunity. Journal of Bacteriology. 2000;182(11):3266-3273.
Sutyak K, Wirawan R, Aroutcheva A, Chikindas M. Isolation of the Bacillus subtilis antimicrobial peptide subtilosin from the dairy product-derived Bacillus amyloliquefaciens. J Appl Microbiol. 2008;104(4):1067-1074.
Flühe L, Knappe T, Gattner M, Schäfer A, Burghaus O, Linne U et al. The radical SAM enzyme AlbA catalyzes thioether bond formation in subtilosin A. Nature Chemical Biology. 2012;8(4):350-357.
Shelburne C, An F, Dholpe V, Ramamoorthy A, Lopatin D, Lantz M. The spectrum of antimicrobial activity of the bacteriocin subtilosin A. Journal of Antimicrobial Chemotherapy. 2006;59(2):297-300.
Sutyak Noll K, Sinko P, Chikindas M. Elucidation of the Molecular Mechanisms of Action of the Natural Antimicrobial Peptide Subtilosin Against the Bacterial Vaginosis-associated Pathogen Gardnerella vaginalis. Probiotics and Antimicrobial Proteins. 2010;3(1):41-47.
