Design, Synthesis and Biological Evaluation of Rose Bengal Analogues as SecA Inhibitors

Abstract

SecA, a key component of bacterial Sec-dependent secretion pathway, is an attractive target for exploring novel antimicrobials. Rose bengal (RB), a polyhalogenated fluorescein derivative, was found from our previous study as a potent SecA inhibitor. Here we describe the synthesis and structure-activity relationships (SAR) of 23 RB analogues that were designed by systematical dissection of RB. Evaluation of these analogues allowed us to establish an initial SAR in SecA inhibition. The antimicrobial effects of these SecA inhibitors are confirmed in experiments using E. coli and B. subtilis.

Monitoring channel activities of proteoliposomes with SecA and Cx26 gap junction in single oocytes

“…These limitations may explain why, as far as we know, no bacterial channel has previously been expressed in the oocytes; the proteo-liposome injection may allow future studies of other bacterial channels. Moreover, the semi-physiological assays of channel activity in the oocytes allow the assessments of functional activities of SecA homologs from other bacteria and inhibitors [25,29] that otherwise are not available. Another advantage of proteoliposome injection is the ability to reconstitute with interacting membrane complexes.…”

“…The SecA-mediated channel activity in oocytes requires the presence of functional SecA and precursors, as well as bacterial membranes [4]. The channel activity is inhibited by the ATP analog AMP-PCP and by the SecA inhibitors azide and Rose Bengal [4,25]. However, channels composed of SecA-liposomes alone are less efficient, requiring larger amounts of SecA and ATP-Mg 2+ for activity, and losing signal peptide specificity [23].…”

Design, syntheses and evaluation of 4-oxo-5-cyano thiouracils as SecA inhibitors

“…More recently RB analogs were developed as potent SecA inhibitors. 33 A recent review summarizes all SecA inhibitors reported in the literature. 34 We have continued our structural optimization efforts on the benzothiazole derivatives to afford different classes of pyrimidine (thiouracil) analogs and Figure 1 summarizes major inhibitors obtained in going from virtual screening hit to the latest inhibitors.…”

Mechanisms of Rose Bengal inhibition on SecA ATPase and ion channel activities

“…Previously, we screened a series of compounds including fluorescein analogs using a truncated form of SecA EcN68 which has higher intrinsic activity and is more sensitive to inhibitors [21,24,25,26]. We have found Rose Bengal (RB) to be an effective SecA inhibitor at sub-micromolar for SecA-mediated translocation ATPase and protein translocation [21].…”

“…However, azide does not affect SecA intrinsic ATPase activity [20]. Other SecA inhibitors have been reported [24,25,26]. Rose Bengal (RB) is the first reported sub-micromolar inhibitor in ATPase activities and protein translocation [21].…”