The Bacterial Sec Pathway of Protein Export: Screening and Follow-Up

J Biomol Screen. 2015 Aug;20(7):921-6. doi: 10.1177/1087057115587458. Epub 2015 May 18.

Abstract

Most noncytoplasmic bacterial proteins are exported through the SecYEG channel in the cytoplasmic membrane. This channel and its associated proteins, collectively referred to as the Sec pathway, have strong appeal as a possible antibiotic drug target, yet progress toward new drugs targeting this pathway has been slow, perhaps due partly to many researchers' focus on a single component, the SecA ATPase. Here we report on a pathway-based screen in which beta-galactosidase (β-gal) activity is trapped in the cytoplasm of Escherichia coli cells if translocation through SecYEG is impaired. Several hit compounds passed a counterscreen distinguishing between β-gal overexpression and impaired β-gal export. However, the most extensively characterized hit gave limited E. coli growth inhibition (EC(50) ≥ 400 µM), and growth inhibition could not be unambiguously linked to the compound's effect on the Sec pathway. Our study and others underscore the challenges of finding potent druglike hits against this otherwise promising drug target.

Keywords: SecE; SecG; SecY; drug development; protein translocation; translocase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / metabolism
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bacterial Secretion Systems*
  • Dose-Response Relationship, Drug
  • Drug Discovery / methods
  • Gene Expression / drug effects
  • High-Throughput Screening Assays
  • Protein Transport / drug effects
  • Small Molecule Libraries
  • beta-Galactosidase / genetics
  • beta-Galactosidase / metabolism

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Bacterial Secretion Systems
  • Small Molecule Libraries
  • beta-Galactosidase