title: Biphasic actions of SecA inhibitors on Prl/Sec suppressors: Possible physiological roles of SecA-only channels.
abstract: SecA is an essential component in the bacterial Sec-dependent protein translocation process. We previously showed that in addition to the ubiquitous, high-affinity SecYEG-SecDF·YajC protein translocation channel, there is a low-affinity SecA-only channel that elicits ion channel activity and promotes protein translocation. The SecA-only channels are less efficient, and like Prl suppressors, lack signal peptide specificity; they function in the absence of signal peptides. The presence of SecYEG-SecDF·YajC alters the sensitivity of ATPase inhibitor Rose Bengal. In this study, we found that the suppressor membranes are much more resistant to inhibition by Rose Bengal. Similar results have been found for a SecA-specific inhibitor. Moreover, biphasic responses of inhibition of ion current and protein translocation activities were observed for many PrlA/SecY and PrlG/SecE suppressor membranes, with a low IC50value similar to that of the SecA-only channels and a very high IC50. However, the suppressor strains are as sensitive to the inhibitor as the parental strain, suggesting that SecA-only channels have some essential physiological function(s) in the cells that are inhibited by the specific SecA inhibitor.
authors.affiliation: Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Ying-Hsin
authors.initials: YH
authors.lastname: Hsieh
authors.affiliation: Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Jinshan
authors.initials: J
authors.lastname: Jin
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Chaofeng
authors.initials: C
authors.lastname: Dai
authors.affiliation: Department of Biology, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Chun
authors.initials: C
authors.lastname: Jiang
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA.
authors.forename: Binghe
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Biology, Georgia State University, Atlanta, GA 30303, USA; Center for Biotechnology and Drug Design, Georgia State University, Atlanta, GA 30303, USA. Electronic address: biopct@gsu.edu.
authors.forename: Phang C
authors.initials: PC
authors.lastname: Tai
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology*; D012395:Rose Bengal / Q000008:administration & dosage*; D000069816:SEC Translocation Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D000069816:SEC Translocation Channels; C065493:SecE protein, E coli; D012395:Rose Bengal; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins
keywords: Biphasic responses; Prl suppressors; SecA inhibitor; SecA-only channels