Stoichiometry and mechanistic implications of the MacAB-TolC tripartite efflux pump
Journal Article
·
· Biochemical and Biophysical Research Communications
- Department of Agricultural Biotechnology, Center for Food Safety and Toxicology, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826 (Korea, Republic of)
- Department of Life Science, Chung-Ang University, Seoul 06974 (Korea, Republic of)
- School of Biological Sciences, The University of Auckland, Auckland 1010 (New Zealand)
- Electron Microscopy Research Center, Korea Basic Science Institute, Chungcheongbukdo 28119 (Korea, Republic of)
Highlights: • The exact stoichiometry of the MacAB-TolC pump was confirmed. • Structural comparison provides a mechanism for MacA-dependent MacB activation. • Improving understanding of the regulatory mechanisms of other efflux pumps. The MacAB-TolC tripartite efflux pump is involved in resistance to macrolide antibiotics and secretion of protein toxins in many Gram-negative bacteria. The pump spans the entire cell envelope and operates by expelling substances to extracellular space. X-ray crystal and electron microscopic structures have revealed the funnel-like MacA hexamer in the periplasmic space and the cylindrical TolC trimer. Nonetheless, the inner membrane transporter MacB still remains ambiguous in terms of its oligomeric state in the functional complex. In this study, we purified a stable binary complex using a fusion protein of MacA and MacB of Escherichia coli, and then supplemented MacA to meet the correct stoichiometry between the two proteins. The result demonstrated that MacB is a homodimer in the complex, which is consistent with results from the recent complex structure using cryo-electron microscopy single particle analysis. Structural comparison with the previously reported MacB periplasmic domain structure suggests a molecular mechanism for regulation of the activity of MacB via an interaction between the MacB periplasmic domain and MacA. Our results provide a better understanding of the tripartite pumps at the molecular level.
- OSTI ID:
- 22897547
- Journal Information:
- Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 3-4 Vol. 494; ISSN BBRCA9; ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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