Development of a Microemulsion Formulation for Antimicrobial SecA Inhibitors

Abstract

In our previous study, we have identified five antimicrobial small molecules via structure based design, which inhibit SecA of Candidatus Liberibacter asiaticus (Las). SecA is a critical protein translocase ATPase subunit and is involved in pre-protein translocation across and integration into the cellular membrane in bacteria. In this study, eleven compounds were identified using similarity search method based on the five lead SecA inhibitors identified previously. The identified SecA inhibitors have poor aqueous solubility. Thus a microemulsion master mix (MMX) was developed to address the solubility issue and for application of the antimicrobials. MMX consists of N-methyl-2-pyrrolidone and dimethyl sulfoxide as solvent and co-solvent, as well as polyoxyethylated castor oil, polyalkylene glycol, and polyoxyethylene tridecyl ether phosphate as surfactants. MMX has significantly improved the solubility of SecA inhibitors and has no or little phytotoxic effects at concentrations less than 5.0% (v/v). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the SecA inhibitors and streptomycin against eight bacteria including Agrobacterium tumefaciens, Liberibacter crescens, Rhizobium etli, Bradyrhizobium japonicum, Mesorhizobium loti, and Sinorhizobium meliloti phylogenetically related to Las were determined using the broth microdilution method. MIC and MBC results showed that the 16 SecA inhibitors have antibacterial activities comparable to that of streptomycin. Overall, we have identified 11 potent SecA inhibitors using similarity search method. We have developed a microemulsion formulation for SecA inhibitors which improved the antimicrobial activities of SecA inhibitors.

The impact of Cymbopogon martinii essential oil on Cutibacterium (formerly Propionibacterium) acnes strains and its interaction with keratinocytes

“…FemB, which maps close to femA, is also involved in the expression of this resistance Preprotein translocase subunit SecA is a peripheral membrane ATPase and part of the Sec protein translocase complex, which has central role in coupling the hydrolysis of ATP to the transfer of proteins into and across the cell membrane, serving as an ATP‐driven molecular motor driving the stepwise translocation of polypeptide chains essential to bacterial growth across the membrane . SecA is a conserved and essential protein in all bacteria; hence, it is considered as a promising target for development of antibacterials …”

Understanding the Physiology of <b><i>Liberibacter asiaticus</i></b>: An Overview of the Demonstrated Molecular Mechanisms

“…The general secretory (Sec) pathway translocates unfolded proteins across the cytoplasmic membrane, leading to either a secreted protein or a protein integrated into the membrane [Akula et al, 2011[Akula et al, , 2012Hu et al, 2016;Manting and Driessen, 2000]. The SecA protein, which exhibits ATPase activity, is the subunit of this system that drives the protein translocation [Van den Berg et al, 2004;Economou and Wickner, 1994].…”

“…The 5 most effective compounds from the in vitro assay were tested for antimicrobial activity against Agrobacterium tumefaciens and were determined to be suitable candidates [Akula et al, 2012]. From these five compounds, a new similarity search was conducted to find 11 compounds for testing [Dean, 1994;Hu et al, 2016;Willett et al, 1998]. Since these compounds have poor aqueous solubility, a micro-emulsion was developed for application [Hu et al, 2016].…”

“…From these five compounds, a new similarity search was conducted to find 11 compounds for testing [Dean, 1994;Hu et al, 2016;Willett et al, 1998]. Since these compounds have poor aqueous solubility, a micro-emulsion was developed for application [Hu et al, 2016]. The minimum inhibitory concentration and minimum bactericidal concentration of the inhibitors was assessed with 8 bacteria (including L. crescens, A. tumefaciens, and Bradyrhizobium japonicum).…”

“…The results obtained were similar to those described for streptomycin. The result of this study was the identification of potent SecA inhibitors as well as a microemulsion formula for improved application [Hu et al, 2016].…”